Kevin Jiménez-Lara, Paleomammalogist and Paleobiogeographer

Kevin taking photographs of a fossil anteater skull deposited at the fossil mammal collections at the Field Museum in Chicago, IL.

First, let me introduce myself. I am a Colombian PhD student at the National University of La Plata, Argentina. My research is focused on the evolution of xenartrans, mammals that include armadillos, sloths, and anteaters.

Since I was a child, I have had a strong fascination to learn about nature. For that reason, I loved (and I still do love) reading a lot and watching documentaries about science, wildlife, meteorological phenomena, the history of the Earth, the history of the Universe, astrophysical theories and hypotheses, and other similar topics. Science has an amazing explanatory power, and that has always been what I like most about it. Science allows us to know our place in the Universe.

Following my vocation, I studied biology in college. Although during my undergrad there were many disciplines that caught my attention, the only one that enamored me was the study of extinct life forms, i.e. paleobiology. At first glance, it is not easy to explain why I wanted to be a paleobiologist, since there are very few Colombian paleobiologists and institutions that teach paleobiology and/or develop paleobiological research in my home country. However, studying the unique history of evolution of living beings seemed not only a noble, respectable activity, but it also became a passion that I believe will always accompany me as long as I live. Paleobiology has formed the basis of my life in the professional field, and also in a personal, philosophical sense.

Kevin doing paleontological prospecting and fossil collection in the La Venta area of southwestern Colombia. In this area some of the most important fossil assemblages of tropical continental vertebrates can be found.

To perform research in paleobiology in a country located in the intertropical belt of the planet (near the equator) and characterized as one of the most biologically diverse areas on Earth poses great challenges and opportunities. On the one hand, there is little or no state support to study paleobiology as a consequence of socio-historical development. In addition, there are limitations related to logistics in regions that are difficult to access due their geographic location and/or security features. We also face scarcity of continuous outcrops of sedimentary rocks where fossils can be found. Often, as a result of climatic factors and abundant vegetation (plant life), fossils are poorly preserved (however, sometimes, they are exquisitely preserved!). But these limitations are largely compensated by huge opportunities. Fossils from the tropics are exceptionally valuable. They document innumerable evolutionary stories that can help explain one of the most disturbing questions for many biologists: why is there a tendency in different groups of living organisms to present greater diversity in the intertropical zone compared to other regions on Earth, such as in higher latitudes?

Paleobiology in the tropics is very necessary because of the generalized geographic bias in research of many extinct organisms and periods of Earth’s history. Namely, most research on these topics has been conducted in Europe and North America. In Colombia, paleontological field expeditions and studies have yielded surprising findings, including, of course, our flagship fossil organism (in my opinion): Titanoboa (Titanoboa cerrejonensis). For all those who do not know it, this snake lived approximately 60 million years ago in the extreme north of Colombia (Guajira peninsula), and its most surprising feature is its size and body mass. Titanoboa measured about 13 meters in length and could exceed one metric ton in weight. That makes it the largest known snake of all time!

Artists’ rendition of Titanoboa in its natural habitat, a very warm and humid tropical forest in La Guajira, northern Colombia, around 60 million years ago. Other reptiles of this time period were also giants, such as crocodiles and turtles.  Image by Jason Bourque.

I contribute to tropical paleobiology by studying fossil xenartrans (armadillos, sloths, and anteaters), particularly those that lived in northern South America and southern Central America. I seek to clarify questions on evolutionary/phylogenetic relationships between extinct representatives of these charismatic mammals and, at the same time, to reconstruct historic changes in their geographical distributions (where they lived through time).

Why is it important to study extinct armadillos, sloths, and anteaters? There are many reasons, but my favorite is that they are animals whose origin and evolution are closely related to great-magnitude abiotic (non-biological) events and processes (such as climate changes and tectonic events). Through tens of millions of years, abiotic factors shaped their biology and ecology to configure the xenartrans in one of the most peculiar mammals that existed during the Cenozoic (the last 65 million years). Have you seen how strange some armadillos look when they roll into a ball, or the very slow movements of a three-toed sloth, or the long tubular snout of a giant anteater? If you have not seen this, you should check out the videos linked in the previous sentence. But in the fossil record we know even more bizarre features of xenartrans than we see in living species. For example, several species of giant sloths used to swim (yes, you read it right, ‘swim’) in littoral zones (areas close to the beach) of western South America around 5 million years ago! Is that not mind-bending?

Several species of the giant sloth genus Thalassocnus could swim in shallow marine habitats off the west coast of South America (Peru and Chile) during the late Miocene-Pliocene (7-4 million years ago). Paleobiologists know this primarily from studies on anatomical adaptations to swimming indicated from the animal’s bone structure. Image by Roman Uchytel.

Xenartrans constitute an outstanding study model on how Earth and life evolve together, from their evolutionary differentiation ~98 million years ago, possibly triggered by the geographic separation of Africa and South America, until their colonization of North America during the last 9 million years in the environmental framework of the Panama Isthmus uplift and the Last Great Glaciation. This makes xenartrans interesting organisms to study evolutionary patterns and processes of high complexity in the tropics.

I am particularly interested on the evolutionary implications (diversification) of dispersal (or movement) events of xenartrans from northern South America to North America (including its ancient Central American peninsula) during geologic intervals which immediately precede the definitive formation of the Isthmus of Panama. Long distance dispersal through a shallow sea, like that which existed between southern Central America and northwestern South America before the complete isthmus emergence, is one of the least understood biogeographic phenomena. The explanatory mechanism of long-distance dispersal allows for disjunct distributions and for us to more comprehensively understand the subtle interaction between distinctive faunas of contiguous areas.

In order to fulfill my general research objective, it is necessary to work hard in determining identities and affinities of Middle-Miocene to Pliocene (15-2 million years old) xenartrans of the aforementioned regions, including not only previously collected fossils, but also new findings. In a complementary way, it is required to put identifications in geographic context through faunal similarity/dissimilarity methods. I also use probabilistic biogeographic models (models that use statistics) to infer major distributional patterns and processes of several subgroups of xenartrans, so that we could understand in an analytic, non-strictly traditional narrative way, the changes of their occurrences in space. Finally, long distance dispersal events through poorly suitable environments for most xenartrans, like shallow seas, are approached through locomotive reconstructions to estimate dispersal capacity (vagility).

I want to end this post by giving an important advice to all those who aspire to be scientists. The path to work in science may be, to a greater or lesser extent, long and complex. However, if you remain true to your convictions and strive under a regime of self-discipline, you will not only be a scientist, but also one of the most prominent researchers in your field. Question everything, do not firmly hold onto hypothesis that have little associated evidence. And, above all, write, write to clarify in your mind many issues related to your research.

To learn more about Kevin and his research, check out his blog called ‘Caribe Prehistorico’. To find this post in Spanish, head to Kevin’s blog by clicking here.

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