As was the case with many other animals I learned about when I was younger, I believed that there was only one kind of animal called a tapir. Most popular books aimed at children don't spend much (if any) time on taxonomy or diversity, so there was no need for the authors of such books to explain that presently there exist four species of tapir in the tropical regions of the world; Baird's tapir (Tapirus bairdii), the mountain tapir (Tapirus pinchaque), and the Brazilian tapir (Tapirus terrestris) in South & Central America and the Malayan tapir (Tapirus indicus) in Southeast Asia. The existence of the Malayan tapir, an animal commonly seen at zoos, proved to be a second shock. I had previously been told that tapirs lived in the jungles of South America; what was Tapirus indicus doing in southeast Asia?
Like many other extant large mammal species, tapirs previously existed over a much greater portion of the globe than they presently inhabit. In order to understand the present range of tapirs, though, we need to know something about the evolutionary history and biogeography of tapirs, a subject of natural history that has been somewhat difficult to discern as it is not one of the areas of greatest interest among researchers. The following post represents what I've been able to glean from a few papers, although I must admit that they did not generally directly provide the answers I was looking for.
According to what is presently understood, the extant genus of tapirs (Tapirus) first appeared in North America during the middle Miocene, about 11.8 to 9 million years ago. This was likely an immigration from Asia, but the genus did not spread to South America until the time of the Great American Biotic Interchange across the isthmus at what is now Panama about 3 million years ago (Ferrero & Noriega, 2007). The earliest known tapirs from South America, specifically from Argentina, have been dated of being of Pleistocene age, about 1.806 to 0.3 million years old, but being that the area now called Argentina is in the southern part of the continent the arrival of Tapirus in South America certainly occurred earlier. If the arrival date for Tapirus in North America just mentioned is accurate, though, the spread of tapirs through North America must have been rapid as by about 9.5 to 7.5 million years ago (the Miocene) the large form Tapirus webbi was present in Florida.
The short summary provided in the Ferrero & Noriega paper is somewhat confusing (at least to someone like me, who is learning about this on the fly) when older fossil evidence is considered, however. Relatives of tapirs (and rhinoceros) were known in North America much earlier, and during the Wasatchian (about 55.5 to 50.5 million years ago) at least two tapiromorphs (the tapiromorpha including Rhinocerotoidea and Tapiroidea, or rhinos and tapirs) called Homogalax and Isectolophus (of the extinct family isectolophidae) were present. They were small and did not look like anything living today, though, representing a more generalized perrisodactyl form similar to that of Hyracotherium. By the Oligocene, 32 to 30.5 million years ago, the tapirid Colodon was exhibiting the kind of skull morphology that would have allowed Colodon to have a flexible proboscis like modern tapirs, a feature that appears to be very derived for the time period and puts Colodon closer to Tapirus than was originally expected.
Tapirs existed elsewhere in the world during the past as well. According to a summary of tapir diversification by Radinsky (1969), tapiroids experienced a high degree of diversification during the Eocene and were well-represented in North America, Asia, and Europe. During this time several groups of tapiroids may have emerged, including the Tapiridae to which the living tapirs belong (other groups, like the aforementioned isectolophidae, eventually died out), although at the time of Radinsky's paper the oldest members of the tapiridae were Oligocene in age. In Europe there were the lophiodontidae, another tapiroid family, that appeared in the early Eocene but disappeared by the close of the Eocene, but Asia was the staging group for an even more extensive radiation of tapiroids. Members of the families Deperetellidae and Lophialetidae were present by the late Eocene, marked by molar specializations that also made the genera Rhodopagus and Indolophus stand out, respectively.
There's a big gap between the Eocene and the present, though, and a I feel frustrated that I'm not able to bring this post to a more satisfactory conclusion. Where did tapirs originate? When did they migrate and to where? What happened to the much greater diversity that has gone extinct? How, exactly, did the Asian species become isolated from the Central & South American species? I was hoping to answer some of these questions at the outset, but I have either missed some important papers on this topic (highly likely) or the biogeography of extinct & extant tapirs is something that hasn't received very much attention.
References;
Colbert, M.W. (2005) "The Facial Skeleton of the Early Oligocene Colodon (Perissodactyla, Tapiroidea).", Palaeontologia Electronica, Vol. 8 (1).
Ferrero, B.S.; Noriega, J.I. (2007) "A New Upper Pleistocene Tapir from Argentina: Remarks on the Phylogenetics and Diversification of Neotropical Tapiridae." Journal of Vertebrate Paleontology, Vol. 27(2), pp. 504-511
Holbrook, L.T.; Lucas, S.G.; Emry, R.J. (2004) "Skulls of the Eocene Perissodactyls (Mammalia) Homogalax and Isectolophus." Journal of Vertebrate Paleontology, Vol. 24 (4), pp. 951-956
Hulbert, R.C., Jr. (2005) "Late Miocene Tapirus (Mammalia, Perissodactylia) from Florida, With Description of a New Species, Tapirus webbi." Bulletin of the Florida Museum of Natural History, Vol. 45(4), pp. 465-494
Radinsky, L.B. (1969) "The Early Evolution of the Perissodactyla." Evolution, Vol. 23 (2), pp.308-328
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Despite their poor fossil record, tapirs are undeniably awesome.
It looks like the information available on the subject has (don't say it) tapired off!
Thank you, thank you, I'll be here all week.
Then there was that basal tapiromorph from Myanmar...Eocene? And Heptodon from Eocene Wyoming. Tapirus occurred in China through the Plio-Pleistocene so it seems we have relict tropical populations of a genus which once ranged through most of east Asia and the New World...that, or they paddled across the Pacific a la Kon Tiki!
It looks like you've done a good job of synthesizing the available information in a short space. Tapirs (Miocene, if I remember) also lived in Europe. It's gratifying and interesting to see anyone talking about tapir evolution at all. I believe that the real problem is not lack of interest (though there is that, too), but lack of clarity (and perhaps lack of clarity does translate back into lack of interest). It's easy to get stuck, and hard to conclude much that is meaningful or clear in order to make a presentation or write a paper trying to show a chronology. This probably discourages people who might otherwise be interested in pursuing the subject in school.
I haven't kept up on the reading, so I won't try to be specific, but the last time I spoke with an expert (Dr. Matt Colbert) about paleotapirs, there were two main factors that I remember making it hard to follow their evolution:
1) There is so much we don't know yet because the fossil record is so sparse. Tapirs today are not herd animals, and tapirs of the past may not have been, either. At best, they may live in pairs or the smallest family groups, and even then they may not travel closely together. Unlike the horse family, and with the notable exception of the Gray fossil beds and some Pleistocene finds in Florida, it's hard to find tapir fossils because they did not die in groups large enough to make them easy to locate. It's also been suggested that the type of terrain they prefer is not conducive to the making of fossils.
2) Tapir evolution seems to be about as confusing as it gets, with branches upon branches, many of which died out, entire species being described rightly or wrongly from a single fossil tooth. There's a lot of speculation on such events as the existence and use of certain land bridges, when they were used and in which direction early tapir relatives crossed them; there were probably multiple crossings in various directions, so there's a lot of wandering that cannot be documented. I don't think you missed much. Last I heard, the evidence simply hasn't been found to clarify the movements and solidify the picture of how these animals ended up where and how they did. I believe it was still in question about whether the ancestral line originated in Asia or in North America, but I think the consensus was that it was probably Asia. From their cradle of origin, there may have been crossing, evolution, then re-crossing, die-outs, more evolution, radiating multiple times, etc. Much or most of this activity has not ended up in the fossil record known to us at this point.
Just to make it all more interesting, the early genetic findings (Ashley, et al) seemed to conflict with morphological evidence regarding the question of how the South American species were related to each other. For instance, which is more advanced, the mountain or lowland tapir? If you look at the feet and the presumed evolution of the foot it becomes even more confusing. But the tapir questions are also exciting. I think there's a whole brave new world out there for tapir studies.
Thanks for an enjoyable post. If you read German, please e-mail me. If there is no link on this comment, contact me via tapirback dot com.
Sheryl
Creationists state that tapirs have always been tapirs. darwinist Kathleen Hunt lists tapir varieties and then states they are evolutionarily related. The onus is on her to show exactly how. Meanwhile, fossil tapirs have been found that are allegedly 50 m.y.o. â but still tapirs.
Editor Allaby, M. (1992, Oxford U. Press) does not say Lophiodontidae (ceratomorph) is transitional to modern tapirs. Mike Benton (2005) only shows a skull of Heptodon (p. 347) but does not discuss it, let alone calling it transitional.
Both Hunt and Colbert can say only that Protapirus is a probable descendent.
Windarr; I see you come to use from the Institute for Creation Research. I would say, then, that the onus is on you to provide evidence that "tapirs have always been tapirs." I notice, for instance, that you do not cit the "allegedly 50 m.y.o." tapir. That would be an interesting specimen to discuss, if it exists, but how can I take the evidence you put forward seriously if it is presented as hearsay?
Unfortunately tapirs are not a "sexy" group of animals that attracts much attention (this is a problem with many fossil mammal groups), but even though there are questions yet to be solved I see no reason to doubt that tapirs have evolved. If tapirs have been in stasis since the Ypresian and did not evolve from any earlier forms, as you intimate, that requires some pretty substantial evidence.
According to Dr. Matthew Colbert, tapirs have evolved in a significant way as recently as about the last one million years. The elongated proboscis, which we all know and love, seems to be a feature of the last million or so years. Until that time, the structure of the skull did not allow for the muscles that support that most obvious extension. Additionally, the feet of each species have a recognizably different structure. Speciation in the Americas (3 species) is apparently relatively new (certainly the adaptations for high mountains vs. low jungles are new) and probably took place completely or largely after the Panamanian land bridge became usable 2-3 million years ago. Observation of the feet gives rise to interesting questions that are still unanswered and little studied.
By the way, I think tapirs are very sexy, but I know your meaning, and it's unfortunate. There are as few mountain tapirs left on Earth as giant pandas (about 2,300 to 2,500), and who knows or cares? They breed better than the pandas, but they have all the habitat issues to deal with that most endangered species face.
Sheryl
pls,
i will like to known at least 7 reason why tapirs are found in asia and in south america.
thanks.
why are tapirs found in south america and asia.
*Hearsay" you say? . . . fossil tapirs have been found that are allegedly *55 million year old* â but still tapirs (*The earliest fossil tapir dates to the early Oligocene (about 30 million years), and Eocene rocks from as early as 55 million years ago contain a wide range of tapir-like animals, and they have changed little since (Taylor 2007)* - âTapirâ New World Encyclopedia, natural history section.
*they have changed little since* that's not macroevolution (darwin's infamous descent with modification), but only minor variation.
I'm sorry Frank, but that just is not good enough. Citing an encyclopedia, itself a summary of other materials that are not sourced in your comment, does not prove that point that tapirs as we know them today have existed since the Eocene.
On top of that, "they have changed little since" is a weaselly phrase that is subjective. You provide no examples and no specifics. As I documented in this post tapirs evolved from Hyracotherium-like perissodactyls which were quite distinct from tapirs as we know them today. And even if tapirs from different ages seem similar that is still consistent with evolutionary theory; not all species are required to change drastically, and there are many "persistent types" that preserve what we might now view as archaic body plans.
Again, if there were tapirs in the Eocene that were precisely like living tapirs the onus is on you to provide primary evidence, not citations from encyclopedias. Likewise, if there is some barrier to evolution beyond a certain point it is up to you to show what that is. I don't think you can or have much desire to. I understand that young earth creationism is based upon an allegiance to a particular interpretation of the Bible first and not to actually understanding nature as it is. As such I doubt we're going to find any common ground here given that I am arguing from science and your position is embedded entirely in your faith.
Although tapirs are evolutionarily conservative, this shouldn't be taken to mean that they haven't changed *at all* through time. Pleistocene tapirs from the American southwest differ in many dental and skeletal respects from those in the southeast, and all of the above differ from earlier fossil tapirs as well as living tapirs. But the differences are subtle, and sample sizes are generally very small, as noted in the main post; so quantifying these differences will take more fossils and more time. Nevertheless, the distinctions are real, and suggesting that tapirs haven't changed through time is nonsense. It's also cherry picking, effectively pretending that all the many, many, many other lineages that *did* change markedly during the same span of geologic time are somehow irrelevant.
In fact, from the perspective of evolution, tapirs present a truly fascinating sidelight on the whole evolutionary process -- particularly in that they are so closely related to horses, a group that is the (literal) poster child of evolution. To have two closely-related animals respond so differently to evolutionary pressures through geologic time -- horses diversifying and exploring new niches, tapirs remaining conservative -- captures a lot of the wonder and beauty and scope of the potential of the evolutionary process. (I often like to contrast the lineages of the animals: horses as "evolution in action", tapirs as "evolution inaction". But I have to be careful to note that "inaction" in this context is a relative term, and doesn't imply that tapirs didn't evolve.)