June 6 was International Ungulate Day, and numerous preoccupations have made me very late to finishing what was supposed to be timely recognition of a notable zoological holiday (many zoos and conservation foundations commemorate this day, so no I’m not just making it up). Since then, it has remained in the static position of a draft which has been somewhat nagging to me. I also began to expand this post in an unexpected direction, to the extent that I feel it necessary to split into two articles, with the forthcoming one being a musing on conservation at a time of dietary shift. This first article acts as a sort of homage to hoofed mammal lineages across the globe, in which I share some personal photographs and lesser known information that I’ve come across.
Spanning from a childhood obsession with cattle to the many hours my family and I have spent observing elk, ungulates have played an integral role in my life and have often been the primary source from which I gained an appreciation for biodiversity. While many belittle ungulates as boring, placid animals that do little more than graze and provide meals for carnivores, those who work and live with these animals can attest to their charismatic nature and profound ecological importance. I suspect that the aforementioned perspective is one founded in an anthropocentric lack of concern for these animals, as they provided more fuel than competition or danger to our species’ expansion. The diversity of the ungulates is tremendous: from tiny duikers slinking cryptically through deep African bush, to massive and culturally distinct orcas coursing through the water as they strategically hunt their prey. I must note that the term ‘ungulate’ seems to have largely fallen out of use in the scientific literature, with some specialists now considering it to merely function as a form taxon or folk taxon rather than a technical grouping. Referring to cetartiodactyls, perissodactyls, and paenungulates is more proper but, for the sake of International *Ungulate* Day, we can let it slide for now.Read More »
Two pygmy hippos (Choeropsis liberiensis) photographed at the Columbus Zoo by yours truly. The evolutionary origin of such mammals has been long unknown, although a recent study in Nature Communications proposes an answer.
A new paper published in the journal Nature Communications has shed crucial light on the ancestry of Africa’s sub-Saharan semiaquatic giant, the hippopotamus. The origins of these animals have long been shrouded in ambiguity but, according to the recent study, can now be definitively placed with the fossil ungulate family Anthracotheriidae. First found in coal deposits, the anthracotheres were aquatic browsers dating back to the late Eocene in Asia and North America.1 Anthracotheres were among the first animals to colonize Africa, although their range was quite diverse throughout the Oligocene and Miocene epochs.1 Morphological features such as the flaring snout, wide heavy feet, hippo-like lower jaw, cetacean-like premolars, and prominent tusks of anthracotheres like Elomeryx and Merycopotamus have been cited in support of a link with Hippopotamidae and Whippomorpha (the clade uniting whales and hippos) as a whole.1,2 The swamp-dwelling tendency of anthracotheres indicated by the presence of their fossil remains in remnant coal seams likely hints at what stimulated differences in morphology and specilization between the otherwise closely related whales and hippos. Stem-whales most probably evolved in coastal environments promoting a carnivorous diet whereas the anthracotherian hippo-progenitors inhabited habitats in which they were restricted to feeding on aquatic plants. As some extant ungulates like pigs occasionally exploit a carnivorous diet, it is not too difficult to imagine stem-whales adopting this trait under restrictive ecological pressures. While fossil stem-cetaceans are numerous and well documented, the ancestry of the ‘river horse’ has been quite the enigma with ghost lineages remaining between the known anthracothere lineages and the oldest fossil hippopotamus. However, the fossil material described in the Nature Communications publication may help to bridge this paleozoological gap.Read More »
Illustration of Perupithecus ucayaliensis by Jorge González
Arguably one of the most appropriate nicknames for the continent Africa is that of ‘The Mother Continent’, a name owing to the fact that our own Mitochondrial Eve can be traced to this location. However, Homo sapiens was not the only primate species to derive out of Africa. A paper recently published in the journal Nature has revealed new fossil material which sheds light on the origins of South America’s iconic monkey species. Read More »
Illustration of the compelling Cambaytherium thewissi by Elaine Kasmer.
As reported on the Science Daily website, John Hopkins University researchers excavating fossils at the edge of a coal mine in India have recently made a discovery which yields revelations on the origins of odd-toed ungulates. Although past research has traced the presence of these animals back to the early Eocene epoch fifty-six million years ago, details on their earlier evolution is shrouded in mystery. The odd-toed ungulates, classified in the order Perissodactyla, include modern day horses and rhinos and are distinguished from other orders due to their uneven number of toes and unique digestive system. Following the proposition of perissodactyls having their origins in Western India, the John Hopkins University research team took to Eocene sediments in this region and unearthed several remains of the little-known ungulate Cambaytherium thewissi. According to these researchers, the teeth, number of sacral vertebrae, and hand and feet bones of Cambaytherium suggest that it is the species most like a common ancestor to all members of Perissodactyla yet discovered. Apart from filling an evolutionary gap, this finding also supports the notion that a diverse number of early mammal groups might have evolved in India while it was still an isolated island continent. This isolation would allow the groups, which included lemur-like primates and both perissodactyls and the even-toed artiodactyls, to evolve without competition from other Paleocene animals. As detailed in Dr. Donald Prothero and Dr. Robert Shoch’s Horns, Tusks, and Flippers: The Evolution of Hoofed Mammals (a book I recently purchased which has rekindled my strong interest in the ungulates), several scientists have previously suggested that India acted as a sort of “Noah’s Ark” which allowed the dispersal of these groups to the rest of the globe following its collision with Asia at the start of the Eocene. The sudden presence of some mammal genera such as the chevrotain-like artiodactyl ancestor Diacodexis in Eocene sediments of Europe and North America without evolutionary precedent certainly suggests that such a hypothesis is more than plausible. The recent Cambaytherium discoveries have apparently yielded “the first concrete evidence” to support this hypothesis, and thus hold even more interesting implications as to the evolution of significant early mammal groups. It is my hope that future research from the aforementioned John Hopkins University researchers who are continuing their work at nearby mines will reveal more exciting data on the evolutionary history of ungulates and other primitive mammal groups.
Tim Morris‘ illustration of the ancestral artiodactyl Diacodexis, quite fittingly referred to as a “bunny deer” by some.
Your typical gray seal, Halichoerus grypus, a hunter of small cetaceans? (Source)
Following the regular discovery of mutilated harbor porpoise carcasses on Dutch beaches since 2003, a group of biologists began a ten year investigation into the situation’s cause.1 The usual suspects of boat propellers or hostile fishermen were dismissed after the deaths regularly continued their toll, and the enigma continued until a group of Belgian researchers came to a startling conclusion.1 In 2012, these researchers took note of apparent bite marks present in some of the wounds inflicted upon the thousands of porpoise carcasses.1 These matched the canine teeth of an unexpected yet certainly capable mammalian predator: the gray seal Halichoerus grypus. With bulls reaching up to almost eleven feet in length and weighing as much as 310 kilograms this was no huge surprise, especially considering their being relatives of animals like the formidable leopard seal. Further examination of the carcasses showed the marks of pinniped claws and signs of the seals having gone after the nourishment of a porpoise’s blubber1, yet the proposition was still subject to some debate.