STL Science Center

STL Science Center

21 April 2018

Pets Everywhere

We have discussed the origins of a large number of what are now very popular pets. We have looked at the origins of dogs, cats, rabbits, reptiles, fish, horses, turtles, and a lot of other animals. One group we have not looked at that has, at least recently, been more regularly miniaturized and taken from the farm to the living room in many areas: the domestic pig. Belonging to the family Suidae, the domesticated pig has a complicated and long lineage. The domesticated pig is in the genus Sus, a group of animals ranging back to the Miocene, though pigs of the family Suidae are certainly a considerable deal older, dating back to the Oligocene.

Picking pigs to discuss is actually a little more difficult than one mine imagine; there are variable sources of information on fossil pigs and there is actually a lot less information, in total, on fossil pigs than one might imagine as well. Many fossil pigs are known entirely from their teeth and a number are known from their skulls and teeth together. Regardless of how much is known of each fossil pig, there is not a great deal written about any fossil pigs online. There are a number of articles on Enteldonts, but these large artiodactyls are not actually a group of pigs. One pig that has a small internet presence, and we can use as a model for talking about pigs at large, is Strozzi's Pig (Sus strozzi). This pig was very porcine, pig-like, and, as is the case in many wild suids, Strozzi's Pig looked very much like a wild boar or a warthog. Strozzi's Pig was a Mediterranean animal, distantly related to the suids of Africa and closely related to its counterparts from Europe and Asia, which contributed to the displacement and eventual extinction of Strozzi's Pig.

19 April 2018

Not So Tiny

We saw earlier this week that Ray Harryhausen made a very nice stopmotion Eohippus for the film The Valley of Gwangi. The reason that the horse was so small is that it was a common misconception that the horse was the size of a Fox Terrier. Many sources have mentioned this size issue many times, but the ultimate source appears to be, according to Stephen Jay Gould, a description of Eohippus written by Henry Fairfield Osborn. It was Gould's opinion that Osborn was excited about the idea of a horse similar in size to a dog and that he was vague in his metaphors to fox hunting when describing the small horse Eohippus. Osborn's comparisons and metaphors make Eohippus out to be a 15 in tall 19 lb horse (the size of a Fox Terrier, obviously); however, Eohippus is approximately 24 inches tall and weighed approximately 50 lbs. There is a difference in the way these animals are measured as well; dogs and horses are both measured from the ground to their withers, the caudal aspect of the shoulders; however, horses typically have a little more soft tissue (muscle and/or fat depending on the breed of dog or horse) than dogs in this area. This is only a problem in comparing the two similarly sized animals in that Eohippus is lacking in the soft tissue area; either way it is still taller than a Fox Terrier. Unfortunately, this sizeable lie is the largest claim to fame, for most people, for Eohippus. It was, of course, also the first recognizable horse, making it an important fossil animal in the history of not only horses, but human beings and, arguably, a large portion of the globe and all of its life. For those more interested in the impact that the descendants of Eohippus have had on the world I recommend starting with this article from Khan Academy.

17 April 2018

The Ever Popular Shrunken Horse

If anyone has ever seen a documentary on the evolution of horses they have most likely seen or heard Bruce MacFadden. They may not have known it, but Dr. MacFadden has, for over 30 years now, been one of the premier horse evolution researchers in the world. Therefore, if one were to search for scientific articles on or mentioning Eohippus they could not, and certainly should not, be amazed when the first two results are MacFadden papers from the 1980s on the size of Eohippus and dental evolution using Eohippus as a vehicle for the discussion (and arguments for evolution based on horses too). There are more recent articles as well, of course, including Froelich's systematics paper on Eocene horses and even a description of museum mounted specimens by G. G. Simpson from 1932 (we all know by now I love reading older scientific articles so of course there was going to be at least one!).

16 April 2018

Prancing Forest Pony

Coursera is a website that has many free courses from different sources, including a number of universities. One course, on horse care, has a video detailing some of the finer points of horse evolution. This video discusses Eohippus and other early horses, so it is a good starting point for any day with a number of videos on early horses. Aside from this, Eohippus is not much of a screen start. The small horses did have one "starring" role in the 1969 movie Valley of Gwangi. Built by Ray Harryhausen, the small model horses were far smaller than they would have been in real life, but they are still adorably stop-motion animated in great detail.

14 April 2018

Dawn of the Horses

©Charles R. Knight
Possibly the most synonymized taxon in the entirety of paleontology, Hyracotherium angustidens was named by E. D. Cope in 1875. In 1876 O. C. Marsh described a similar taxon, naming it Eohippus validus. When Clive Forster noted similarities between the genera in 1932 he reassigned E. validus to the senior genus Hyracotherium. When Hyracotherium was redescribed as a paraphyletic taxon in recent years it was noted that H. angustidens and H. validus were identical species, and Marsh's specific name was considered junior to Cope's, but was considered the only valid genus of the two. Therefore, after all of these taxonomic twists, the animal considered the earliest and smallest of the equid lineage was officially renamed Eohippus angustidens. The official list of synonyms for Eohippus stands at 13 junior names, 3 of which are actually subspecies of other synonyms. Regardless, the small horses are interesting in many ways and, more importantly, are animals that have not been discussed here in full, and are therefore deserving of some time in the spotlight.

12 April 2018

People Love Cats

Pseudaelurus may be the most important cat in the entire family line that almost no one has ever heard of. Aside from ending the North American "cat-gap," Pseudaelurus is an important genus because these cats represent the last common ancestors of a diverse array of cats and "near cats." Saber-tooth cats, as a general term, technically fall out of the family line to cats before true felids. As an evolutionary grade, a group of taxa united by shared morphology, Pseudaelurus contains both felids and the true saber-tooth cats (Machairodontinae). This is why Pseudalurus is referred to as the last common ancestor to both saber-tooths and felids; the term "saber-tooth cat" can be extremely confusing because of the true and false labels in addition to the phylogenetic maze of carnivorans in which they settle out. For more information, I encourage everyone to read these articles on false saber tooths at ThoughtCo and Prehistoric Wildlife.

The genus Pseudaelurus has been separated and lumped a number of times over the years. However, the most recent phylogenetic studies (Werdelin et al. 2010 and Piras et al. 2013) have split Pseudalurus over three lineages definitively (unless someone comes along in the future to lump them again). The new genera include Hyperailurictis, Styriofelis, and Miopanther. These each represent a distinct lineage leading to the extinct lineage of American Hyperailurictis felids and the Styriofelis/Miopanther group (including both the extinct lineage of European Styriofelis felids and the extant Felinae which includes domesticated and wild cats). The third lineage retained the name Pseudaelurus and led to the extinct Machairodontinae, the true saber-tooth cats.

10 April 2018

Papers That Are Fond of Cats

Pseudaelurus is important in all lineages of felidae because it is the last common ancestor of many different types of cats, but it is also important to people that know, love, and study cats because of this as well. Additionally, Pseudaelurus is the genus of cat that bridged the so-called "cat-gap" in North American fossil history. Tom Rothwell is a paleontologist that knows a lot about Pseudaelurus and the cat-gap. Rothwell has written papers on the phylogeny of Pseudaelurus cats in North America and he has described new species within the genus as well. There are other paleontologists writing papers about Pseudaelurus of course. Papers on Pseudaelurus can be found from as far back as at least 1954 and at least one article on dentition and the skull was written in the 1930s. However, new remains of Pseudaelurus species are described on a somewhat regular basis; clearly this was a genus that was very successful and must have been quite varied to have so many different species identified.