De la tierra al agua

Algunos de los mamíferos marinos que existen hoy día, como los cetáceos, sirénidos y pinípedos*, están tan adaptados a una vida en el agua, que puede que se nos haga difícil relacionarlos con sus parientes más cercanos los cuales son terrestres. Aquí les voy a dar un poco de información sobre la evidencia que existe hasta ahora sobre la trancición de la tierra al agua en estos grupos de organismos.

*(cetáceos = ballenas y delfines; sirénidos = manatí y dugong; pinípedos = focas, morsas y leones marinos).

Cetáceos

Las ballenas que conocemos hoy día se pueden dividir en dos grupos, los odontocetos y misticetos. Los odontocetos se caracterizan por tener dientes y utilizar ecolocalización; los misticetos se caracterizan por tener barbas en lugar de dientes (ambos grupos tienen otras adaptaciones que discutiré en otro momento). Ejemplos de odontocetos son las orcas y delfines; las misticetos incluyen ballenas azules y ballenas pigmeas.

Estudios moleculares idicaban que las ballenas evolucionaron de los artiodáctilos – grupo que incluye a los cerdos, hipopótamos, camellos, vacas, ovejas, etc – (Graur & Higgins, 1994; Shimamura et al., 1997). Estudios morfológicos solían indicar que los cetáceos habían evolucionado de los mesoniquios – un grupo extinto de mamíferos terrestres carnívoros – (Luo & Gingerich, 1999). En parte, la razón para que existiera esa discrepancia sobre los orígenes de los cetáceos era que los fósiles de cetáceos más antiguos consistían de formas ya completamente adaptadas a una vida en el agua, o solamente se conocía el cráneo. Ya esto ha sido resuelto.

En el 2001, dos grupos de paleontólogos publicaron trabajos donde describían fósiles de ballenas primitivas, incluyendo partes del postcráneo que demostraban que estas estaban relacionadas a los artiodáctilos (Gingerich et al., 2001; Thewissen et al., 2001). Gingerich y su equipo recuperaron los restos de dos Artiocetus clavis y Rhodocetus balochistanensis, mientras que el grupo de Thewissen recuperaron los de Ichthyolestes pinfoldi y Pakicetus attocki (ilustración adyacente de Pakicetus por Carl Buell, tomado de la página del Thewissen Lab); entre las partes que encontraron incluía uno de los huesos del tobillo, el astrágalo, que fue la pieza clave para determinar que los cetáceos evolucionaron de los artiodáctilos. Todos estos fósiles fueron encontrado en sedimentos que datan del Eoceno Medio (entre 49 y 41 millones de años). Recientemente, Thewissen et al. (2007) describen los restos postcraneales del artiodáctilo primitivo, Indohyus, y demuestran que este era un animal con adaptaciones acuáticas y provee evidencia adicional sobre el origen de los cetáceos. (Una reconstrucción magnífica de Indohyus puede ser vista aquí.)

Sirénidos

Los parientes vivos más cercanos de los manatíes y dugones son los elefantes, esto está evidenciado tanto por información morfológica como genética (Seiffert, 2007; Tabuce et al. 2007). EL origen de los sirénidos fue en África alrededor de 54 millones de años donde compartieron un ancestro en común con los elefantes. Interesantemente, los fósiles de sirénidos más primitivos se han encontrado en Jamaica, lo cual demuestra que muy temprano en su historia evolutiva ya estaban adaptados a una vida en ambientes marinos. Durante mucho tiempo, el sirénido fósil más primitivo era Prorastomus sirenoides encontrado en Jamaica en depósitos que datan de 51-49 millones de años (Owen, 1855; Savage et al., 1994). Sin embargo, el postcráneo de este organismo todavía sigue siendo desconocido.

Otro sirénido fósil, también de Jamaica, pero encontrado en depósitos un poco más jovenes (49-45 millones de años), fue descrito por Domning (2001). Este nuevo fósil, llamado Pezosiren portelli (ilustración arriba tomada de Domning, 2001), consiste de partes del cráneo y postcráneo. Los restos postcraneales de Pezosiren incluye los brazos, patas, pelvis y casi toda la columna vertebral; en conjunto, estos indican que este organismo era capaz de soportar su cuerpo fuera del agua a la misma vez, también tiene adaptaciones acuáticas como costillas agrandadas y densas y la fosa nasal retractada (Domning, 2001). Esta combinación de adaptaciones indican que este organismo pasaba tiempo tanto dentro como fuera del agua.

Pinípedos

Estudios morfológicos y moleculares demuestran que los pinípedos pertenecen a un grupo de mamíferos llamado arctoideos (Deméré et al., 2003), que además de los pinípedos, incluyen a los osos (úrsidos), mustelas (mustélidos), mapaches (prociónidos) y zorrilos (mefítidos) entre otros. Sin embargo, el origen de los pinípedos de alguno de estos otros arctoideos no es clara y diferentes estudios ponen a los pinípedos originándose de un ancestro en común con los mustélidos o con los úrsidos (Deméré et al., 2003). Otros expertos en la materia apoyan la idea que los pinípedos tienen origenes separados, las focas evolucionando de un ancestro en común con los mustélidos y los leones marinos y morsas con los úrsido (Uhen, 2007 y referencias ahí). Cualquiera que sea el grupo del cual los pinípedos se originaron, algo que solo se podrá aclarar a medida que se descubren más fósiles, sabemos que se originan de un organismo terrestre. Interesantemente, fósiles de pinípedos que demuestren una morfología transicional, entre completamente marino / completamente terrestre, no fueron encontrados hasta hace poco.

El reciente descubrimiento de Puijila darwini en sedimentos lacustrinos depositados entre 23-21 millones de años, nos da una idea sobre la morfología de los primeros pinípedos (Rybczynski et al., 2009). Aunque ya se han econtrado restos de pinípedos más antiguos, Enaliarctos tedfordi y E. barnesi encontrados en rocas que datan de entre 28.5-23.8 en Oregon (Deméré et al., 2003), estos ya presentan adaptaciones a una vida marina como las que vemos en las especies modernas, lo cual significa que los pinípedos deben haber evolucionado previo a esta fecha. Así que aunque Puijila (ilustración adyacente tomada de Rybczynski et al., 2009) es más joven, su importancia resta en que su morfología es la más primitiva de los pinípedos conocidos, proveyendo además evidencia sobre los posibles pasos evolutivos que se llevaron a cabo en la transición de la tierra al agua en este grupo de mamíferos.

Gracias a MPT y YFS por ayudar con la gramática.

Página oficial de Puijila

Puijila en National Geographic

English version here.

Referencias

Deméré, T. A., A. Berta & P. J. Adams. 2003. Pinnipedomorph evolutionary biogeography. Bulletin of the American Museum of Natural History 279:32-76.

Domning, D. P. 2001. The earliest known fully quadrupedal sirenian. Nature 413:625-627.

Gingerich, P. D., M. ul Haq, I. S. Zalmout, I. H. Khan & M. S. Malkani. 2001. Origin of whales from early artiodactyls: hands and feet of Eocene Protocetidae from Pakistan. Science 293:2239-2242.

Graur, D. & D. G. Higgins. 1994. Molecular evidence for the inclusion of cetaceans within the order Artiodactyla. Molecular Biology and Evolution 11(3):357-364.

Luo, Z. & P. D. Gingerich. 1999. Terrestrial Mesonychia to aquatic Cetacea: transformation of the basicranium and evolution of hearing in whales. University of Michigan Papers on Paleontology 31:1-98.

Owen, R. 1855. On the fossil skull of a mammal (Prorastomus sirenoides, Owen), from the island of Jamaica. Quarterly Journal of the Geological Society of London 11:541-543.

Rybczynski, N., M. R. Dawson & R. H. Tedford. 2009. A semi-aquatic Arctic mammalian carnivore from the Miocene epoch and origin of Pinnipedia. Nature 458:1021-102.

Savage, R. J. G., D. P. Domning & J. G. M. Thewissen. 1994. Fossil Sirenia of the West Atlantic and Caribbean region. V. Prorastomus sirenoides Owen, 1855. Journal of Vertebrate Paleontology 14(3):427-449.

Seiffert, E. R. 2007. A new estimate of afrotherian phylogeny based on simultaneous analysis of genomic, morphological, and fossil evidence. BMC Ecolutionary Biology 7:224 Open access

Shimamura, M., H. Yasue, K. Ohshima, H. Abe, H. Kato, T. Kishiro, M. Goto, I. Munechika & N. Okada. 1997. Molecular evidence from retroposons that whales form a clade within even-toed ungulates. Nature 388:666-670.

Tabuce, R., L. Marivaux, M. Adaci, M. Bensalah, J.-L. Hartenberger, M. Mahboubi, F. Mebrouk, P. Tafforeau & J.-J. Jaeger. 2007. Early Tertiary mammals from North Africa reinforce the molecular Afrotheria clade. Proceedings of the Royal Society B 274:1159-1166.

Thewissen, J. G. M., E. M. Williams, L. J. Roe & S. T. Hussain. 2001. Skeletons of terrestrial cetaceans and the relationship of whales to artiodactyls. Nature 413:277-281.

Thewissen, J. G. M., L. N. Cooper, M. T. Clementz, S. Bajpai & B. N. Tiwari. 2007. Whales originated from aquatic artiodactyls in the Eocene epoch of India. Nature 450:1190-1195.

Uhen, M. D. 2007. Evolution of marine mammals: back to the sea after 300 million years. Anatomical Record 290:514-522.

Domningia and other Indian sirenians

Over the last 12 years a number of fossil sirenians have been described from Eocene through Miocene deposits from India. This has not stopped as, new taxa are been discovered and described; much of the effort is spearheaded by Sunil Bajpai of the Dept. of Earth Sciences, Indian Institute of Technology and J. G. M. Thewissen of the Dept. of Anatomy and Neurobiology, NEOUCOM (Thewissen Lab). So far all the fossil sirenians from India have been collected from outcrops in the Kachchh District near the western coast of the country; this area is better known for primitive cetaceans such as remingtonocetids (Kumar & Sahni, 1986).

Eocene

The oldest Indian sirenians come from the Middle Eocene Harudi Formation; a total of three species representing two families: Protosiren sp. (Protosirenidae), Eotheroides babiae, Eosiren sp. (Dugongidae, Halitheriinae) (Bajpai et al. 2006). Other species belonging to those genera are found in Eocene deposits in northern Africa (Domning, 1996) indicating a southern Tethyan influence, better referred to as the Indo-African Region of the Tethys Realm (Harzhauser et al. 2002). There should be more on Eocene sirenians from India, sometime this year.

Oligocene

So far only one Oligocene sirenian is known from this region, Bharatisiren indica (Dugongidae, Dugonginae) from the Maniyara Fort Formation of Late Oligocene age (Bajpai et al. 2006). This is the oldest dugongine found in this region, and it is as old as the dugongines, Crenatosiren olseni and Dioplotherium manigualti from the Western Atlantic (Domning, 1989; Domning, 1997) and a new taxon from Puerto Rico. Dugongines are a group that is thought to have evolved in the Western Atlantic and Caribbean Region (Domning, 2001), the occurrence of B. indica seems to point to a latest Eocene or Early Oligocene origin for the group with subsequent trans-Atlantic dispersal to the Indo-African Region. An alternative scenario, is the origin of dugongines in the Mediterranean region of the Tethys Realm with subsequent east and west dispersal, unfortunately no Early or Late Oligocene dugongines are known from this region (the names of the paleobiogeographic areas based on Harzhauser et al. 2002).

Lateral view of the skull of B. indica from Bajpai et al. (2006).

Miocene

During the Early Miocene there seems to have been a radiation of dugongines in this region. With at least two taxa known Bharatisiren kachchhense, Domningia sodhae* from Khari Nadi Formation (Bajpai & Domning, 1997; Thewissen & Bajpai, 2009), and another currently under study, it is an good example of multispecies communities like the ones present in the Western Atlantic and Caribbean Region (Domning, 2001). As you can see in the composite picture below, a notable difference between B. kachchhense and Domningia sodhae is the rostral deflection, which probably reflects different degrees of specializations for bottom feeding (Domning, 2001). They seem to have had similar shape of their tusks, large and more-or-less oval in cross-section, this morphology most likely aided in obtaining large seagrass rhizomes (Domning, 2001; Domning & Beatty, 2007), although probably at different levels due to the differences in rostral deflection. Interestingly, it seems that there were no post-Eocene halitheriines.

*Domningia sodhae was aptly named after Dr. Daryl P. Domning of Howard University, world renowned paleosirenologist, a well deserved recognition.

Lateral view of B. kachchhense (top; from Bajpai & Domning, 1997) and Domningia sodhae (bottom; image reversed, from Thewissen & Bajpai, 2009).

Where are the halitheriines?

So far no post-Eocene halitheriines are known from the Oligocene and Miocene of India, at least two possible explanations come to mind: (1) they were present but no fossils have been found yet, or; (2) they were totally absent. An explanation for the second alternative could be provided by the invertebrate fauna. Based on gastropod fauna it seems that, during the Oligocene, changes in the geological settings in the Tethys Realm led to changes in the ocean currents and what was previously known as the Indo-African Region was subsequently divided into the Mediterranean-Iranian and Western Indian-Eastern African provinces of the Western Tethyan Region (Harzhauser et al. 2002). Subsequently, during the Early Miocene, further fragmentation of the Western Indian-Eastern African Province led to an increase of South-East Asian influence and the formation of the Proto-Western Indian Ocean Province; this separation was further augmented by the closure of the Eastern Mediterranean seaway during the latest Early Miocene (Harzhauser et al. 2002). The progressive isolation of what would become the Proto-Western Indian Ocean Province from a Tethyan influence might have prevented halitheriines from entering the region, especially after the Late Oligocene, leading to specialization and radiation of dugongines in this part of the world.

 References

Bajpai, S. & D. P. Domning. 1997. A new dugongine sirenian from the Early Miocene of India. Journal of Vertebrate Paleontology 17(1):219-228.

Bajpai, S., J. G. M. Thewissen, V. V. Kapur, B. N. Tiwari & A. Sahni. 2006. Eocene and Oligocene sirenians (Mammalia) from Kachchh, India. Journal of Vertebrate Paleontology 26(2):400-410.

Domning, D. P. 1989. Fossil Sirenia of the West Atlantic and Caribbean Region. II. Dioplotherium manigaulti Cope, 1883. Journal of Vertebrate Paleontology 9:415-428.

Domning, D. P. 1996. Bibliography and index of the Sirenia and Desmostylia. Smithsonian Contributions to Paleobiology 80:1-611.

Domning, D. P. 1997. Fossil Sirenia of the West Atlantic and Caribbean Region. VI. Crenatosiren olseni (Reinhart, 1976). Journal of Vertebrate Paleontology 17:397-412.

Domning, D. P. 2001. Sirenians, seagrasses, and Cenozoic ecological change in the Caribbean. Palaeogeography, Palaeoclimatology, Palaeoecology 166:27-50.

Domning, D. P. & B. L. Beatty. 2007. Use of tusks in feeding by dugongid sirenians: observations and tests of hypotheses. The Anatomical Record 290:523-538.

Harzhauser, M., W. E. Piller & F. F. Steininger. 2002. Circum-Mediterranean Oligo-Miocene biogeographic evolution – the gastropods’ point of view. Palaeogeography, Palaeoclimatology, Palaeoecology 183:103-133.

Kumar, K. & A. Sahni. 1986. Remingtonocetus harudiensis, new combination, a Middle Eocene Archeocete (Mammalia, Cetacea) from western Kutch, India. Journal of Vertebrate Paleontology 6(4):326-349.

Thewissen, J. G. M. & S. Bajpai. 2009. A new Miocene sirenian from Kutch, India. Acta Palaeontologica Polonica 54(1):7-13.

Solenodon paradoxus grooved incisors

Keeping up with the previous post, here’s a picture of the mandible of a Hispaniolan Solenodon. Notice that I have made an enlargement of the anterior part, outline in the top picture, to show the groove present on its second incisor. The red lines outline the borders of the groove. The specimen was collected in the Dominican Republic and is in the collection of the Department of Paleobiology at the National Museum of Natural History.

Answers to the mystery critter post

Congratulations to Ville Sinkkonen for guessing correctly the identity of the Marabou stork (Leptoptilos crumeniferus) and the genus of the mystery critter 2, which actually is the Hispaniolan solenodon (Solenodon paradoxus) (full pictures below). I must apologize for taking sooo long in posting the answers, but I’m also adding some interesting facts about this critters, enjoy!!

Marabou storks are scavengers, but will also consume frogs, fish and mice; when stalking prey they rely mainly on their vision, but if needed also by tactolocation (Kahl, 1966). One observation made by Kahl (1966), is that along with other birds, marabou storks will wait near brushfires for escaping or injured prey. The skulls of an interesting group of pterosaurs, the azhdarchids, has been likened to marabou storks and other terrestrial stalkers, which together with other morphological evidence has implication for their paleoecology (Witton & Naish, 2008). More on those interesting pterosaurs here.

In addition to Leptoptilos crumeniferus from sub-Saharan Africa, there are two other species known, Leptoptilos javanicus from South East Asia and L. dubius from South Asia. An extinct larger form, Leptoptilus falconeri, from the Pliocene of Africa and South Asia, stood up to about 2 meters and might have been more terrestrial (had proportionately slightly smaller wings) (Louchart et al. 2005). Other fossil species include L. titan from the Pleistocene of Java and L. richae from the Late Miocene of Tunisia, additional species that have been recognize in the past from Asia or Africa have been synonimized mainly with L. falconeri (Louchart et al. 2005). More recently, Noriega & Cladera (2008) described Leptoptilos patagonicus from the Late Miocene of Argentina. This South American record expands not only the range of the genus, but also of the tribe Leptoptilini (op. cit.). It wouldn’t be surprising if these turn out in similar or younger age deposits around western and/or northern South America.

            Now on to Solenodon. There are only two extant species of solenodons, Solenodon paradoxus and S. cubanus from Hispaniola and Cuba respectively. According to studies on gene sequences of these living species, they seem to have diverged about 76 million years ago from their common ancestor with other eulipotyphlan insectivores, whereas divergence between the two species seem to have occurred about 25 million years ago (Roca et al. 2004). An interesting aspect of the dentition of Solenodon paradoxus is that one of the lower incisors (I₂) has a groove on the lingual side (here), which in the living animal serves for injecting venom (McDowell, 1958). This makes S. paradoxus the only known living mammal with modified dentition for venom delivery. Although this could be used to infer similar adaptation in extinct mammals, caution should be taken when finding extinct mammals with grooved dentition, as the sole presence of a grooved canine or incisor should not be regarded as a definite indication of capabilities of injecting venom into victims (Folinsbee et al. 2007, Orr et al., 2007). If you’re interested in the cranial osteology Solenodon paradoxus there’s a recent publication, Wible (2008), which is very detailed and has very good illustrations.

The fossil record of Solenodon shows that there were at least two other species during the Pleistocene, S. marcanoi and S. arredondoi from Hispaniola and Cuba respectively (Patterson, 1962; Morgan & Ottenwalder, 1993). Older remains, consisting of part of an axial skeleton, were found embedded in amber from the Early to Middle Miocene La Toca Formation of the Dominican Republic; these were described as belonging to a small solenodontid insectivore by MacPhee & Grimaldi (1996).

Solenodon, was not the only insectivore living in the Caribbean region, there was also a closely related form that was found in Cuba, Hispaniola and Puerto Rico, these were the Nesophontes (McDowell, 1958), which will be the subject of a future post.

 

REFERENCES

Folinsbee, K. E., J. Müller & R. R. Reisz. 2007. Canine grooves: morphology, function, and relevance to venom. Journal of Vertebrate Paleontology 27(2):547-551.

Kahl, M. P. 1966. Comparative ethology of the Coconiidae. Part 1. The marabou stork, Leptoptilos crumeniferus (Lesson). Behaviour 27(1-2):76-106.

Louchart, A., P. Vignaud, A. Likius, M. Brunet & T. D. White. 2005. A large extinct marabou stork in African Pliocene hominid sites, and a review of the fossil species of Leptoptilos. Acta Palaeontologica Polonica 50(3):549-563.

MacPhee, R. D. E. & D. A. Grimaldi. 1996. Mammal bones in Dominican Amber. Nature 380:489-490.

McDowell, S. B., Jr. 1958. The Greater Antillean Insectivores. Bulletin of the American Museum of Natural History 115:113-214.

Morgan, G. S. & J. A. Ottenwalder. 1993. A new extinct species of Solenodon (Mammalia: Insectivora: Solenodontidae) from the Late Quaternary of Cuba. Annals of the Carnegie Museum 62(2):151-164.

Noriega, J. I. & G. Cladera. 2008. First record of an extinct marabou stork in the Neogene of South America. Acta Palaeontologica Polonica 53(4):593-600.

Orr, C. M., L. K. Delezene, J. E. Scott, M. W. Tocheri & G. T. Schwartz. 2007. The comparative method and the inference of venom-delivery systems in fossil mammals. Journal of Vertebrate Paleontology 27(2):541-546.

Patterson, B. 1962. An extinct solenodontid insectivore from Hispaniola. Breviora 165:1-11.

Roca, A. L., G. K. Bar-Gal, E. Eizirik, K. M. Helgen, R. Maria, M. S. Springer, S. J. O’Brien & W. J. Murphy. 2004. Mesozoic origin for West Indian insectivores. Nature 429: 649-651.

Wible, J. R. 2008. On the cranial osteology of the Hispaniolan Solenodon, Solenodon paradoxus Brandt, 1833 (Mammalia, Lipotyphla, Solenodontidae). Annals of the Carnegie Museum 77(3):321-402.

Witton, M. P. & D. Naish. 2008. A reappraisal of azhdarchid pterosaur functional morphology and paleoecology. PLoS ONE 3(5):1-16.

Identify the mystery critters/Identifica los animales misteriosos

It’s been a while since I posted something, mostly because of a class that takes away most of my daytime productive hours. So, here’s a brief post on which you will have to figure out what are the critters in the pictures. I’ll be traveling during the weekend but will hopefully have some time to finish a longer post I have been working on, sporadically, for the last month or so. Feel free to post your identification.

Enjoy the pictures and, by the way, Happy Darwin Day!!!

 

Hace tiempo que no “posteo” nada, mayormente debido a una clase que tengo durante mis horas productivas del día. Asi que aquí tienen una entrada breve donde ustedes tratarán de identificar los animales en las fotos. Estaré viajando durante el fin de semana, pero espero sacar tiempo para terminar una entrada un poco más extensa en la cual he estado trabajando esporádicamente durante el último mes. Siéntanse libre de comentar sobre la identificación.

Disfruten las fotos y felíz día de Darwin!!!

Mystery critter 1/animal misterioso 1

Mystery critter 2/animal misterioso 2

A river runs through an Oligocene sea

The subject of this post is about my second and final day of fieldwork in Puerto Rico. Yes, I only managed to get two days of fieldwork because these were actually some very short vacations and on top of that it was very rainy. Anyways, I already wrote about my first day of fieldwork during which I searched for tetrapods in the Late Oligocene Lares Limestone. Now on my second day I went out to one of my favorite localities, herein referred to as Río G. This locality consists of exposures of the Early Oligocene age San Sebastián Formation along the banks of a river (See the picture below with me as scale and outcrops on each side of the river). The exposures along this river are considered as typical of the basal part of this formation (Monroe, 1980). The lithology of this formation is varied, with some layers representing ancient soils, river channels, deltaic deposits as well as marine units. Of course this is all in a sequence that makes sense with the tectonic history and paleogeography of the region, an interesting subject, which I will not touch at this moment, but might be discussed sometime in the future.

Now, some interesting tetrapods have been recovered from this formation, such as the sirenian Caribosiren turneri, described by Reinhart in 1959. Also from this formation are known pelomedusid turtles, which were previously discussed here. From the Río G locality, one of the more recent discoveries is the skull of the gryposuchine gavialid Aktiogavialis puertoricensis (Velez-Juarbe, et al. 2007). Other tetrapods found here, include sirenians, part of a croc axial skeleton and the oldest-but-crappiest rodent fossil from the Caribbean region. Some of these, like the sirenians are part of my thesis project, whereas the others are still awaiting description or for better material to turn up.

Unfortunately, same as with the prospecting in the Lares Limestone, no new or even useful vertebrate fossils were found in Río G. The most interesting fossil I found was a plant fossil that might be a seed or some sort of fruit (see picture below of the seed/fruit together with a schematic drawing – the fossil measures about 27 mm across). If it actually turns out to be a seed/fruit it would not be the first time that plant “megafossils” are found in the San Sebastián Formation; about 88 taxa of plant macrofossils from this formation were described by Sir Arthur Hollick in the 1920’s (Graham, 1996). I have yet to see Hollick’s (1926, 1928) papers; therefore I still don’t know if my fossil is similar to any of the material he described.

Well, at least since Río G is along a body of water, it turned out a nice place to do some bird watching. I have on previous occasions observed some of the birds along this river, with the difference that now I had a camera with a good zoom allowing me to take some nice pictures. The composite picture below include, clockwise beginning with the upper left: male Molothrus bonariensis (shiny cowbird); Butorides striatus (green-backed heron); Egretta caerulea (little blue heron); Actitis macularia (spotted sandpiper, this one has the winter plumage hence the lack of spots).

An interesting fact about the shiny cowbird is that it is an invasive species from South America, first reported from the Caribbean region during the latter half of the 1800’s (Post & Wiley, 1977a). It is also a brood parasite; in Puerto Rico it parasitizes about 16 different species of birds with a preference for the yellow-shouldered blackbird (Agelaius xanthomus) (Post & Wiley, 1977b; Pérez-Rivera, 1986). These are actually bad news as the yellow-shouldered blackbird is an endemic to the Puerto Rico bank.

On the earlier half of the day, while stalking a green-backed heron (Butorides striatus), I was unwillingly reminded to always keep an eye of where I put my feet. The reason was that while trying to stealthily sneak up to see where the bird was standing, I almost ended up stepping on a couple of fairly large green iguanas (Iguana iguana) (see composite picture below)!

This was actually the first time I have seen green iguanas in the wild in this part of the island. Iguanas are an introduced pest in Puerto Rico therefore their occurrence in this locality took me totally by surprise, although I am aware that they are getting more common around the island, specially in the east and north where it is more humid (I believe they are still not present in the drier southern coast or that they are much less common there). Green iguanas are doing really well in Puerto Rico; the reason might be that once they reach an adult size, nothing, except maybe humans, will eat them. Perhaps another reason for their success is that until several thousand years ago there were Anegada rock iguanas (Cyclura pinguis) in Puerto Rico (Pregill, 1981); are then green iguanas just filling in an empty niche left over by the extinction of the Anegada rock iguana from Puerto Rico? This is unlikely; rock iguanas (Cyclura spp.) are adapted to xeric environments, which, unlike today, were present in northern PR during the Pleistocene (Pregill & Olson 1981). This means that the habitat that was occupied by C. pinguis in northern Puerto Rico, no longer exist there (rock iguanas are not the only xeric-adapted tetrapod to go extinct in northern PR [op. cit.]). All I know is that from now on I will have to keep an eye out for green iguanas while doing fieldwork, at least in northern Puerto Rico.

References

Graham, A. 1996. Paleobotany of Puerto Rico-from Arthur Hollick’s (1928) scientific survey paper to the present. Annals of the New York Academy of Sciences 776: 103-114.

Hollick, A. 1926. Fossil walnuts and lignite from Porto Rico. Journal of the New York Botanical Garden 27:223-227.

Hollick, A. 1928. Paleobotany of Porto Rico. Scientific Survey of Porto Rico and the Virgin Islands 7(3):177-393.

Monroe, W. H. 1980. Geology of the middle Tertiary formations of Puerto Rico. US Geological Survey Professional Paper 953:1-93.

Pérez-Rivera, R. A. 1986. Parasitism by the shiny cowbird in the interior parts of Puerto Rico. Journal of Field Ornithology 57(2):99-104.

Post, W. & J. Wiley. 1977a. The shiny cowbird in the West Indies. Condor 79:119-121.

Post, W. & J. Wiley. 1977b. Reproductive interactions of the shiny cowbird and the yellow-shouldered blackbird. Condor 79:176-184.

Pregill, G. K. 1981. Late Pleistocene herpetofaunas from Puerto Rico. University of Kansas Museum of Natural History, Miscellaneous Publications 71:1-72.

Pregill, G. K. & S. L. Olson. 1981. Zoogeography of the West Indian vertebrates in relation to Pleistocene climatic cycles. Annual Review of Ecology and Systematics 12:75-98.

Reinhart, R. H. 1959. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences 36(1):1-146.

Velez-Juarbe, J., C. A. Brochu & H. Santos. 2007. A gharial from the Oligocene of Puerto Rico: transoceanic dispersal in the history of a nonmarine reptile. Proceedings of the Royal Society B 274:1245-1254.

Publicaciones de fósiles de Puerto Rico / Publications on fossils from Puerto Rico

Para esta nota he recopilado un listado de publicaciones que tratan sobre fósiles de Puerto Rico. Por supuesto que el listado está viciado a favor de publicaciones sobre vertebrados fósiles los cuales son mis favoritos o invertebrados con los cuales he trabajado en el pasado. Si conoces referencias adicionales me puedes avisar (a través de correo electrónico o comentarios abajo) para asi añadirlos a la lista. Algunas de las referencias incluso están enlazados su pdf gratis.

For this post I have compiled a list of publications that deals with fossils from Puerto Rico. Of course it is somewhat biased toward vertebrates, which are my favorites or invertebrates on which I have worked on previous occasions. If you know additional references that are not here just let me know (either through emails or comments below) and they will be added. Some of these are linked to their free pdf.

Updated: 25/May/2025

Allen, J. A. 1916. An extinct octodont from the island of Porto Rico, West Indies. Annals of the New York Academy of Sciences 27:17-22.

Anthony, H. E. 1916a. Preliminary diagnosis of an apparently new family of insectivores. Bulletin of the American Museum of Natural History 35(41):725-728.

Anthony, H. E. 1916b. Preliminary report of fossil mammals from Porto Rico, with descriptions of a new genus of ground sloth and two new genera of hystricomorph rodents. Annals of the New York Academy of Sciences 27:193-203.

Anthony, H. E. 1917a. New fossil rodents from Porto Rico, with additional notes on Elasmodontomys obliquus Anthony and Heteropsomys insulans Anthony. Bulletin of the American Museum of Natural History 37(4):183-190.

Anthony, H. E. 1917b. Two new fossil bats from Porto Rico. Bulletin of the American Museum of Natural History 37(19):565-568.

Anthony, H. E. 1918. The indigenous land mammals of Porto Rico, living and extinct. American Museum of Natural History, Memoirs 1(2):329-435.

Anthony, H. E. 1925. Mammals of Porto Rico, living and extinct—Chiroptera and Insectivora. New York Academy of Sciences, Scientific Survey of Porto Rico and the Virgin Islands IX:1–96.

Anthony, H. E. 1926. Mammals of Porto Rico, living and extinct—Rodentia and Edentata. New York Academy of Sciences, Scientific Survey of Porto Rico and the Virgin Islands IX:97–241.

Auffenberg, W. 1967. Notes on West Indian tortoises. Herpetologica 23(1):34-44.

Bandini, A. N., P. O. Baumgartner, K. Flores, P. Dumitrica, C. Hochard, G. M. Stampfli, and S.-J. Jackett. 2011. Aalenian to Cenomanian Radiolaria of the Bermeja Complex (Puerto Rico) and Pacific origin of radiolarites on the Caribbean Plate. Swiss Journal of Geociences 104:367-408.

Banerjee, A., K. Yemane, and A. Johnson. 2000. Foraminiferal biostratigraphy of late Oligocene-Miocene reefal carbonates in southwestern Puerto Rico. Micropaleontology 46(4):327-342.

Barbour, T. 1919. A new rock iguana from Puerto Rico. Proceedings of the Biological Society of Washington 32:145-148.

Bermúdez, P. J., and G. A. Seiglie. 1967. A new genus and species of foraminifer from the early Miocene of Puerto Rico. Tulane Studies in Geology 5:177–179.

Bermúdez, P. J., and G. A. Seiglie. 1970. Age, paleoecology, correlation and foraminifers of the uppermost Tertiary formation of northern Puerto Rico. Caribbean Journal of Science 10:17-33.

Blackburn, D. C., R. M. Keeffe, M. C. Vallejo-Pareja, and J. Velez-Juarbe. 2020. The earliest record of Caribbean frogs: a fossil coquí from Puerto Rico. Biology Letters 16:20190947.

Bonilla-Rodríguez, A. J., L. A. González, J. D. Walker, and H. Santos. 2014. Strontium isotope (87Sr/86Sr) stratigraphy from the Coalcomana-Caprinuloidea rudist assemblage in the Greater Antilles (Puerto Rico, Dominican Republic and Jamaica). Cretaceous Research 50:97-109.

Brochu, C. A., A. M. Nieves-Rivera, J. Velez-Juarbe, J. D. Daza-Vaca and H. Santos. 2007. Tertiary crocodylians from Puerto Rico: evidence for late Tertiary endemic crocodylians in the West Indies? Geobios 40:51-59.

Choate, J. R. and E. C. Birney. 1968. Sub-recent Insectivora and Chiroptera from Puerto Rico, with the description of a new bat of the genus Stenoderma. Journal of Mammalogy 49(3):400-412.

Cobban, W. A., and G. R. Scott. 1988. Occurrence of the early Cretaceous Ammonite Venezoliceras in Puerto Rico. U.S. Geological Survey Bulletin 1837:D1–D2.

Coryell, H. N., and V. Ohlsen. 1929. Fossil corals of Porto Rico, with descriptions also of a few recent species. New York Academy of Sciences, Scientific Survey of Porto Rico and the Virgin Islands 3(3):169-236.

Cutress, B. M. 1980. Cretaceous and Tertiary Cidaroida (Echinodermata, Echinoidea) of the Caribbean area. Bulletin of American Paleontology 77:1-221.

Da Cunha, L., L. W. Viñola-López, R. D. E. MacPhee, L. Kerber, J. Vélez-Juarbe, P.-O. Antoine, M. Boivin, L. Hautier, R. Lebrun, L. Marivaux, and P.-H. Fabre. 2023. The inner ear of caviomorph rodents: phylogenetic implications and application to extinct West Indian taxa. Journal of Mammalian Evolution 30:1155–1176.

Domning, D. P. and O. A. Aguilera. 2008. Fossil Sirenia of the West Atlantic and Caribbean region. VIII. Nanosiren garciae, gen. et sp. nov. and Nanosiren sanchezi, sp. nov. Journal of Vertebrate Paleontology 28(2):479-500.

Donovan, S. K., S. N. Nielsen, J. Velez-Juarbe, R. W. Portell. 2019. The isocrinine crinoid Isselicrinus Rovereto from the Paleogene of the Americas. Swiss Journal of Palaeontology 138:317-324.

Edinger, E. N., and M. J. Risk. 1994. Oligocene-Miocene extinction and geographic restriction of Caribbean corals: roles of turbidity, temperature, and nutrients. PALAIOS 9(6):576-598.

Flemming, C. and R. D. E. MacPhee. 1999. Redetermination of holotype of Isolobodon portoricensis (Rodentia, Capromyidae), with notes on recent mammalian extinctions in Puerto Rico. American Museum Novitates 3278:1-11.

Frank, E. F. and R. Benson. 1998. Vertebrate paleontology of Mona Island, Puerto Rico. Journal of Cave and Karst Studies 60:103-106.

Frost, S. H., J. L. Harbour, D. K. Beach, M. J. Realini, and P. M. Harris. 1983. Oligocene reef track development, southwestern Puerto Rico. Sedimenta 9:1-144.

Gaffney, E. S., and R. C. Wood. 2002. Bairdemys, a new side-necked turtle (Pelomedusoides: Podocnemididae) from the Miocene of the Caribbean. American Museum Novitates 3359:1-28.

Galloway, J. J., and C. E. Hemingway. 1941. The Tertiary Foraminifera of Porto Rico. New York Academy of Sciences, Scientific Survey of Porto Rico and the Virgin Islands 3(4):275-491.

Gordon, W. A. 1960. The age of the middle Tertiary rocks of northwestern Puerto Rico. Second Caribbean Geological Conference, Transactions. 87–90.

Gordon, W. A. 1961. Distribution of Foraminifera in the middle Tertiary San Sebastián-Isabela section, Puerto Rico. Caribbean Journal of Sciences 1(2):48–58.

Gordon, W. A. 1961. Miocene Foraminifera from the Lajas Valley, Southwest Puerto Rico. Journal of Paleontology 35(3):610-619.

Gordon, W. A. 1961. Planktonic foraminifera and the correlation of the middle Tertiary rocks of Puerto Rico. Micropaleontology 7(4):451-460.

Gordon, W. A. 1963. Middle Tertiary echinoids of Puerto Rico. Journal of Paleontology 37(3):628-642.

Gordon, W. A. 1966. Two crab species from the middle Tertiary of Puerto Rico. Transactions of the Third Caribbean Geological Conference, Kingston, Jamaica, 2nd-11th April, 1962:184-186.

Graham, A. 1996. Paleobotany of Puerto Rico-from Arthur Hollick’s (1928) scientific survey paper to the present. Annals of the New York Academy of Sciences 776: 103-114.

Graham, A. and D. M. Jarzen. 1969. Studies in neotropical botany. I. The Oligocene communities of Puerto Rico. Annals of the Missouri Botanical Garden 56:308-357.

Herrera, F., S. R. Manchester, J. Velez-Juarbe, and C. Jaramillo. 2014. Phytogeographic history of the Humiriaceae (Part 2). International Journal of Plant Sciences 175:828-840.

Hollick, A. 1924. A review of the fossil flora of the West Indies, with description of new species. Bulletin of the New York Botanical Garden 12:259–323.

Hollick, A. 1926. Fossil walnuts and lignite from Porto Rico. Journal of the New York Botanical Garden 27:223-227.

Hollick, A. 1928. Paleobotany of Porto Rico. Scientific Survey of Porto Rico and the Virgin Islands 7(3):177-393.

Howell, B. F. 1966. New Upper Cretaceous sponge from Puerto Rico. Journal of Paleontology 40(1):207-209.

Hubbard, B. 1920. Tertiary Mollusca from the Lares district, Porto Rico. New York Academy of Sciences, Scientific Survey of Porto Rico and the Virgin Islands 3(2):79-164.

Hubbard, B. 1923. The geology of the Lares District, Porto Rico. New York Academy of Science Survey of Porto Rico and the Virgin Islands, 2, 115 p.

Iturralde-Vinent, M. A. 2001. Geology of the amber-bearing deposits of the Greater Antilles. Caribbean Journal of Science 37(3-4):141-167.

Iturralde-Vinent, M. A. and E. Harstein. 1998. Miocene amber and lignitic deposits in Puerto Rico. Caribbean Journal of Science 34:308-312.

Jackson, R. T. 1922. Fossil echini of the West Indies. Carnegie Institution of Washington Publication 306:1-103.

Kauffman, E., and N. F. Sohl. 1974. Structure and evolution of Antillean Cretaceous rudist frameworks. Verhandlungen der naturforschenden Gessellchaft in Basel 84:399–467.

Krijnen, J. P. 1978. Pseudorbitoids from the Parguera Limestone, Puerto Rico, and from the Back Rio Grande Limestone, Jamaica, with remarks on the pseudorbitoidal evolutionary pattern. Geologie en Mijnbouw 57:233–242.

Luque, J., C. E. Schweitzer, W. Santana, R. W. Portell, F. J. Vega, A. A. Klompmaker. 2017. Checklist of fossil decapod crustaceans from Tropical America. Part I: Anomura and Brachyura. Nauplius 25:e2017025.

MacPhee, R.D.E. 2011. Basicranial morphology and relationships of Antillean Heptaxodontidae (Rodentia, Ctenohystrica, Caviomorpha). Bulletin of the American Museum of Natural History 363:1-70.

MacPhee, R.D.E. and M.A. Iturralde-Vinent. 1995. Origin of the Greater Antillean land mammal fauna, 1: new Tertiary fossils from Cuba and Puerto Rico. American Museum Novitates 3141:1-31.

MacPhee, R. D. E. and A. R. Wyss. 1990. Oligo-Miocene vertebrates from Puerto Rico, with a catalog of localities. American Museum Novitates 2965:1-12.

Marivaux, L., J. Velez-Juarbe, and P.-O. Antoine. 2020. 3D models related to the publication: Early Oligocene chinchilloid caviomorphs from Puerto Rico and the initial rodent colonization of the West Indies: 3D models of Oligocene Puerto Rican chinchilloids. MorphoMuseum, Association Palaeovertebrata 6(4):e127. DOI: 10.18563/journal.m3.127

Marivaux, L., J. Velez-Juarbe, and P.O. Antoine. 2021. 3D models related to the publication: An unpredicted ancient colonization of the West Indies by North American rodents: dental evidence of a geomorph from the early Oligocene of Puerto Rico. MorphoMuseum, Association Palaeovertebrata 7:e128. DOI: 10.18563/journal.m3.128

Marivaux, L., L. W. Viñola-López, M. Boivin, L. Da Cunha, P.-H. Fabre, R. Joannes-Boyau, G. Maincent, P. Münch, N. S. Stutz, J. Vélez-Juarbe, and P.-O. Antoine. 2022. Incisor enamel microstructure of West Indian caviomorph hystricognathous rodents (Octodontoidea and Chinchilloidea). Journal of Mammalian Evolution. DOI: 10.1007/s10914-022-09631-7

Marivaux, L., J. Velez-Juarbe, G. Merzeraud, F. Pujos, L. W. Viñola López, M. Boivin, H. Santos-Mercado, E. J. Cruz, A. Grajales, J. Padilla, K. I. Vélez-Rosado, M. Philippon, J.-L. Léticée, P. Münch, and P.-O. Antoine. 2020. Early Oligocene chinchilloid caviomorphs from Puerto Rico and the initial colonization of the West Indies. Proceedings of the Royal Society B 287:20192806.

Marivaux, L., J. Velez-Juarbe, L. W. Viñola López, P.-H. Fabre, F. Pujos, H. Santos-Mercado, E. J. Cruz, A. Grajales Pérez, J. Padilla, K. I. Vélez-Rosado, J.-J. Cornée, M. Philippon, P. Münch, and P.-O. Antoine. 2021. An unpredicted ancient colonization of the West Indies by North American rodents: dental evidence of a geomorph from the early Oligocene of Puerto Rico. Papers in Palaeontology 1–19. DOI: 10.1002/spp2.1388

Matthew, W. D. 1916. New sirenian from the Tertiary of Porto Rico. Annals of the New York Academy of Sciences 27:23-29.

Matthew, W. D. 1918. Affinities and origin of the Antillean mammals. Bulletin of the Geological Society of America 29:657-666.

Matthew, W. D. 1919. Recent discoveries of fossil vertebrates in the West Indies and their bearing on the origin of the Antillean Fauna. Proceedings of the American Philosophical Society 58:161-181.

Mattson, P. H., and E. A. Pessagno, Jr. 1979. Jurassic and Early Cretaceous radiolarians in Puerto Rican ophiolite—Tectonic implications. Geology 7:440–444.

Maury, C. J. 1920. Tertiary Mollusca from Porto Rico and their zonal relations. New York Academy of Sciences, Scientific Survey of Porto Rico and the Virgin Islands 3(1):1-77.

McDowell, S. B. 1958. The Greater Antillean insectivores. Bulletin of the American Museum of Natural History 115:113-214.

McFarlane, D. A. 1999. A note on dimorphism in Nesophontes edithae (Mammalia: Insectivora), an extinct island-shrew from Puerto Rico. Caribbean Journal of Science 35:142-143.

McFarlane, D. A. 1999. Late Quaternary fossil mammals and last occurrence dates from caves at Barahona, Puerto Rico. Caribbean Journal of Science 35(3-4):238-248.

Mitchell, S. F. 2013. Revision of the Antillocaprinidae Mac Gillavry (Hippuritida, Bivalvia) and their position within the Caprinoidea d'Orbigny. Geobios 46:423–446.

Mitchell, S. F. 2020. Exceptionally well-preserved silicified hippuritid rudist bivalves from the lower Maastrichtian of Puerto Rico. Carnets de Géologie 20:333–366.

Mitchell, S. F. 2022. Revision of the hippuritid rudists from the Pozas Formation (upper Santonian/lower to middle Campanian), Puerto Rico, and their evolutionary and stratigraphical significance. Cretaceous Research 138:105289.

Mitchell, S. F., M. Martínez-Colón, R. Ramsook and H. Santos. 2012. A primitive tube-bearing antillocaprinid rudist bivalve, Parasarcolites sohli, sp. nov., from Jamaica and Puerto Rico, West Indies. Cretaceous Research 34:149-153.

Montgomery, H., E. Robinson, J. Saunders, W. Van den Bold. 1991. Paleontology of the Toa Baja #1 well, Puerto Rico. Geophysical Research Letters 18:509-512.

Morgan, G. S. 2001. Patterns of Extinction in West Indian Bats; pp. 369-407 in C. A. Woods and F. E. Sergile (eds.), Biogeography of the West Indies: Patterns and Perspectives, Second Edition. CRC Press, Boca Raton, Florida.

Moussa, M. T. 1974. Tertiary brachiopods from Puerto Rico and their paleontologic and paleoecologic significance. Journal of Paleontology 48(6):1202-1206.

Moussa, M. T., and G. A. Seiglie. 1970. Revision of Mid-Tertiary stratigraphy of Southwestern Puerto Rico. American Association of Petroleum Geologists Bulletin 54:1887–1898.

Nieves-Rivera, A. M. 2007. Paleobotanical notes on mangrove-like plants of Puerto Rico. Interciencia 32:175-179.

Nieves-Rivera, A. M., J. E. Mylroie, and D. A. McFarlane. 1995. Bones of Puffinus lherminieri Lesson (Ages: Procellaridae) and two other vertebrates from Cueva del Agua, Mona Island, Puerto Rico (West Indies). National Speleological Society Bulletin 57:99-102.

Nieves-Rivera, A. M., M. Ruiz-Yantín and M.D Gottfried. 2003. New record of the Lamnid shark Carcharodon megalodon from the Middle Miocene of Puerto Rico. Caribbean Journal of Science 39:223-227.

Nieves-Rivera, Á. M., J. P. Zegarra Vila, C. E. Figuerola Hernández, J. E. García-Hernández, and N. V. Schizas. 2020. Recent and historical explorations of the underwater section of Cueva del Agua, Punta Los Ingleses, Mona Island (Puerto Rico), with a new faunal record. Life: The Excitement of Biology 8(1):4-22.

Olson, S. L. 1974. A new species of Nesotrochis from Hispaniola, with notes on other fossil rails from the West Indies (Aves: Rallidae). Proceedings of the Biological Society of Washington 38:439-450.

Olson, S. L. 1976. A new species of Milvago from Hispaniola, with notes on other fossil caracaras from the West Indies (Aves: Falconiformes). Proceedings of the Biological Society of Washington 88:355-366.

Olson, S. L. 1976. Fossil woodcocks: an extinct species from Puerto Rico and an invalid species from Malta (Aves:Scolopacidae: Scolopax). Biological Society of Washington, Proceedings 89(20):265-274.

Olson, S. L. 1985. Pleistocene birds from Puerto Rico. National Geographic Society Research Reports 18:563-565.

Olson, S. L. 1982. A new species of palm swift (Tachornis: Apodidae) from the Pleistocene of Puerto Rico. The Auk 99:230-235.

Olson, S. L. 2015. History, morphology, and fossil record of the extinct Puerto Rican parakeet Psittacara maugei Souancé. The Wilson Journal of Ornithology 127(1):1-12.

Olson, S. L. and E. J. Maíz López. 2008. New evidence of Ara autochthones from an archeological site in Puerto Rico: a valid species of West Indian macaw of unknown geographic origin (Aves: Psittacidae). Caribbean Journal of Science 44(2):215-222.

Olson, S. L. and M. C. McKitrick. 1981. A new genus and species of emberizine finch from Pleistocene cave deposits in Puerto Rico (Aves: Passeriformes). Journal of Vertebrate Paleontology 1(3/4):279-283.

Olson, S. L. and Á. M. Nieves-Rivera. 2010. Fossil evidence and probable extinction of the greater fishing bat Noctilio leporinus (Chiroptera: Noctilionidae) on Isla de Mona, Puerto Rico. Mastozoología Neotropical 17(1):167-170.

Ortega-Ariza, D., E. K. Franseen, and M. K. Boudagher-Fadel. 2021. Effects of sea level and upwelling on development of a Miocene shallow-water tropical carbonate ramp system, Ponce, Puerto Rico. Journal of Sedimentary Research 91:1227–1256.

Ortega-Ariza, D., E. K. Franseen, H. Santos-Mercado, W. R. Ramírez-Martínez, and E. E. Core-Suárez. 2015. Strontium isotope stratigraphy for Oligocene-Miocene carbonate systems in Puerto Rico and the Dominican Republic: implications for Caribbean processes affecting depositional history. Journal of Geology 123:539-560.

Panuska, B. C., J. M. Mylroie, D. Armentrout, and B. McFarlane. 1998. Magnetostratigraphy of Cueva del Aleman, Isla de Mona, Puerto Rico and the species duration of Audubon's shearwater. Journal of Cave and Karst Studies 60:96-100.

Pearson, P. N. and B. S. Wade. 2009. Taxonomy and stable isotope paleoecology of well-preserved planktonic foraminifera from the uppermost Oligocene of Trinidad. Journal of Foraminiferal Research 39(3):191-217.

Pessagno, E. A., Jr. 1960. Stratigraphy and micropaleontology of the Cretaceous and lower Tertiary of Puerto Rico. Micropaleontology 6(1):87-110.

Pessagno, E. A., Jr. 1961. The micropaleontology and biostratigraphy of the middle Eocene Jacaguas group, Puerto Rico. Micropaleontology 7:351–358.

Pessagno, E. A., Jr. 1962. The Upper Cretaceous stratigraphy and micropaleontology of south-central Puerto Rico. Micropaleontology 8(3):349-368.

Pessagno, E. A., Jr. 1963. Planktonic Foraminifera from the Juana Diaz Formation, Puerto Rico. Micropaleontology 9(1):53-60.

Pessagno, E. A., Jr. 1963. Upper Cretaceous Radiolaria from Puerto Rico. Micropaleontology 9(2):197-214.

Pisera, A., M. Martínez and H. Santos. 2006. Late Cretaceous siliceous sponges from El Rayo Formation, Puerto Rico. Journal of Paleontology 80(3):594-600.

Pregill, G. K. 1981. Late Pleistocene herpetofaunas from Puerto Rico. University of Kansas Museum of Natural History, Miscellaneous Publications 71:1-72.

Pregill, G. K., and S. L. Olson. 1981. Zoogeography of West Indian Vertebrates in relation to Pleistocene climatic cycles. Annual Review of Ecology and Systematics 12:75-98.

Rabell-Cabrero, N. 1914. Notas paleontológicas. Revista de las Antillas 2(1):66-69.

Rabell-Cabrero, N. 1924. Notas sobre algunos escuálidos fósiles de Puerto Rico. Revista Agricultura de Puerto Rico 12:377-384.

Ray, C. E. 1964. The taxonomic status of Heptaxodon and dental ontogeny in Elasmodontomys and Amblyrhiza (Rodentia: Caviomorpha). Bulletin of the Museum of Comparative Zoology 131(5):107-127.

Reinhart, R. H. 1959. A review of the Sirenia and Desmostylia. University of California Publications in Geological Sciences 36(1):1-146.

Reynolds, T. E., K. F. Koopman, and E. E. Williams. 1953. A cave faunule from western Puerto Rico with a discussion of the genus Isolobodon. Breviora 12:1–8.

Sachs, K. N., Jr. 1959. Puerto Rican upper Oligocene larger Foraminifera. Bulletin of American Paleontology 39:399-416.

Sachs, K. N., Jr. 1964. Multilocular embryonts in Lepidocyclina (Eulepidina) undosa Cushman from Puerto Rico. Micropalaeontology 10:323-329.

Sachs, K. N., Jr., and W. A. Gordon. 1962. Stratigraphic distribution of middle Tertiary larger Foraminifera from southern Puerto Rico. Bulletins of American Paleontology 44:5-24.

Schweitzer, C. E., M. A. Iturralde-Vinent, J. L. Hetler and J. Velez-Juarbe. 2006. Oligocene and Miocene Decapods (Thalassinidea and Brachyura) from the Caribbean. Annals of the Carnegie Museum of Natural History 75(2):111-136.

Schweitzer, C. E., J. Velez-Juarbe, M. Martinez, A. Collmar Hull, R. M. Feldmann and H. Santos. 2008. New Cretaceous and Cenozoic decapoda (Crustacea: Thalassinidea, Brachyura) from Puerto Rico, United States Territory. Bulletin of the Mizunami Fossil Museum 34:1-15.

Seiglie, G. A. 1972. A new genus and species of foraminifera from the Tertiary of Puerto Rico. Caribbean Journal of Science 12:115–118.

Seiglie, G. A. 1973. Revision of mid-Tertiary stratigraphy of southwestern Puerto Rico. Bulletin of the American Association of Petroleum Geologists 57:405–406.

Seiglie, G. A., and P. J. Bermúdez. 1969. Informe preliminar sobre los foraminíferos del Terciario del sur de Puerto Rico. Caribbean Journal of Science 9:67-80.

Seiglie, G. A., and M. T. Moussa. 1976. Smaller benthic foraminifera and correlation of the Oligocene-Pliocene rocks in Puerto Rico. Caribbean Geological Conference Transactions 7:255–262.

Seiglie, G. A., K. Grove, and J. A. Rivera. 1976. Revision of some Caribbean Archaiasinae, new genera, species and subspecies. Ecologiae Geologicae Halvetiae 70:855–883.

Sohl, N. F. 1987. Cretaceous gastropods: contrasts between Tethys and the temperate provinces. Journal of Paleontology 61(6):1085–1111.

Sohl, N. F. 1992. Upper Cretaceous gastropods (Fissurellidae, Haliotidae, Scissurellidae) from Puerto Rico and Jamaica. Journal of Paleontology 66(3):414-434.

Sohl, N. F. 1998. Upper Cretaceous trochacean gastropods from Puerto Rico and Jamaica. Palaeontographica Americana 60:1-109.

Sohl, N. F., and H. A. Kollmann. 1985. Cretaceous actaeonellid gastropods from the Western Hemisphere. U.S. Geological Survey Professional Paper 1304:1–104.

Soto-Centeno, J. A., and D. W. Steadman. 2015. Fossils reject climate change as the cause of extinction of Caribbean bats. Scientific Reports 5:7971.

Soto-Centeno, J. A., R. Rodríguez Ramos, P. I. Monico, C. A. Calderón-Acevedo, J. Bernstein, and L. W. Viñola López. 2025. A Holocene bat colony collapse highlights the importance of hot caves in the Caribbean. Biology Letters 21:20240700. DOI: 10.1098/rsbl.2024.0700

Smith, A. G., N. F. Sohl, and E. L. Yochelson. 1968. New upper Cretaceous Amphineura (Mollusca). U.S. Geological Survey Professional Paper 593-G:1–9.

Todd, R., and D. Low. 1976. Smaller Foraminifera from deep wells on Puerto Rico and St. Croix. U.S. Geological Survey Professional Paper 863:1–32.

Turvey, S. T. 2010. Evolution of non-homologous venom delivery systems in West Indian insectivores? Journal of Vertebrate Paleontology 30(4):1294-1299.

Turvey, S. T., F. V. Grady and P. Rye. 2006. A new genus and species of ‘giant hutia’ (Tainotherium valei) from the Quaternary of Puerto Rico: an extinct arboreal quadruped? Journal of Zoology 270:585-594.

Turvey, S. T., J. R. Oliver, Y. M. Narganes Storde and P. Rye. 2007. Late Holocene extinction of Puerto Rican native land mammals. Biology Letters 3:193-196.

van den Bold, W. A. 1965. Middle Tertiary Ostracoda from Northwestern Puerto Rico. Micropaleontology 11(4):381-414.

van den Bold, W. A. 1969. Neogene Ostracoda from southern Puerto Rico: Caribbean Journal of Science 9:117-133.

van den Bold, W. A. 1975. Remarks on Ostracode-bioestratigraphy of the late and middle Tertiary of southwest Puerto Rico. Caribbean Journal of Science 15:31-40.

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