Rhinoceros Giants: A Fresh Look at the Largest Land Mammal Ever

The cover of Rhinoceros Giants, with brilliant artwork by Carl Buell. (Source)

The ungulates are an exceptionally diverse group of mammals, with members having conquered a wide range of niches and even returning to the sea. One of the most interesting representatives of this clade was the impressive fossil perissodactyl Paraceratherium, the focus of a book recently published by Dr. Donald Prothero. Paraceratherium holds the title of the largest terrestrial mammal ever, having stood twenty-two feet tall at the shoulder and outweighing the largest modern elephant by twice its bulk. This animal possessed a skull which could grow to six feet in length and exhibited a pair of conical tusks. Prothero details an intriguing new interpretation of the skull's anatomical features which suggest that this rhinocerotoid would have possessed a form of trunk or proboscis and relatively large ears: striking morphology illustrated in the vibrant cover of this book. Rhinoceros Giants provides an exciting narrative on both the discovery and evolutionary history of Paraceratherium, shedding much light on the diverse past of the rhinoceros. I feel that a book of the nature as this one has been well-warranted for quite some time now. Prothero helps to clear up controversy over the proper name for these behemoths, and provides a better understanding of the ecology and potential life behavior of the indricotheres in detail not matched by the documentaries which helped Paraceratherium gain its fame. Rhinoceros Giants gives the unprecedented textual attention that this remarkable fossil mammal deserves.

Fossil Find May Conclude Controversy Over Hippo Origins

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.

New Fossils Reveal The Mother Continent for South American Monkeys

Illustration of Perupithecus ucayaliensis by Jorge González

Arguably one of the best 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. In 2010, a team of paleontologists led by Los Angeles County Natural History Museum curator Dr. Ken Campbell uncovered the teeth of three novel extinct primates in the east Peruvian Amazon. The first specimen took two years to identify as a result of its anatomy being distinct from that of modern day South American monkeys, the platyrrhines. The date of this species was traced to the Eocene epoch approximately 36 million years ago, making it ten million years older than any other fossil platyrrhine known. As a result, the newly named Perupithecus ucayaliensis is considered by scientists as a significant piece of the puzzle that is the evolutionary history of South American monkeys.

New Findings Suggest Odd-Toed Ungulates Originated On Continental "Noah's Ark"

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 brings 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.