Monday, March 21, 2016

Monday Miocene Primate: Pliopithecus antiquus

Pliopithecus antiquus was among the first fossil primates ever unearthed. Discovered by Édouard Lartet in 1837 in Sansan, France, the original specimen was named by Henri-Marie Blainville in 1839, but was not officially nominated as a taxon until 1849 by Paul Gervais.

Among pliopithecoids, P. antiquus is one of the most complete specimens. The type specimen consists of a nearly complete mandible with missing rami. All of the lower teeth are present, with only the crowns missing from the right canine and left second incisor. P. antiquus remains one of the smallest pliopithecoids discovered, its small dental size being among its most identifying features.

P. antiquus was a widespread species known from multiple sites in France as well as sites in Germany, Poland, and Switzerland. Based on biostratigraphy, P. antiquus is known primarily from fossil strata assigned to MN6 (15 million years ago), but t has been suggested that P. antiquus may have persisted to MN9 (11 million years ago).

Monday, March 7, 2016

Miocene Monday Primate: Victoriapithecus macinnesi

With an assigned fossil range from 12.5 to 19 million years ago Victoriapithecus macinnesi is one of the oldest known fossil  monkeys (only recently supplanted by Nsungwepithecus gunnelli at 25 MA). Victoriapithecus predates the emergence of old world monkeys, and as a part of the larger Victoriapithecidae family, it represents a sister taxon to Cercopithecidae (old world monkeys).

Unlike most modern Cercopithecids, who are largely arboreal, Victoriapithecus was terrestrial primate that lived off a diet of hard fruits and seeds. Given the phylogenetic position of this taxon at the base of the Cercopithecidae lineage, some authors have suggested that the common ancestor of all old world monkeys may have passed through a terrestrial stage before returning to the trees.
From Gonzales et al. (2015).
More recently researchers at Duke University have suggested that although Victoriapithecus had a relatively small brain, it was surprisingly wrinkled. A highly wrinkled brain, as opposed to a smooth brain, increases the surface area over which neurons can fire, suggesting increased cognitive capacity. So even though Victoriapithecus was a small monkey (3-5 kg), it was probably pretty crafty. If your species is going to stick around and remain largely unchanged for close to 7 million years, being able to outsmart your competitors is a necessary survival skill. Maybe staying on the ground and away from the arboreal habitat of the Miocene apes was one of best ideas Victoriapithecus ever had. 

Wednesday, March 2, 2016

Sunken taxa: Telanthropus capensis

In 1949 Robert Broom and John T. Robinson described "A New Type of Fossil Man" from Swartkrans cave, South Africa. The fossil used to designate this newly described species, Telanthropus capensis, was a nearly complete mandible (below).

Broom and Robinson had previously described another hominin species from Swartkrans, Paranthropus crassidens (later synonmized with Paranthropus robustus), but the Telanthropus jaw was significantly different. It more closely resembled modern humans, as opposed to the large, robust mandible and megadont teeth of Paranthropus. In their initial diagnosis Broom and Robinson suggested it was morphologically similar to what they referred to as "Heidelberg Man" (aka the Mauer Jaw).
Left: Telanthropus capensis, Right: JT Robinson and Robert Broom
Following their intial publication, Robinson and Broom found a few more specimens which they included in the Telanthropus capensis hypodigm. The following year Broom (1950) came to the conclusion all of the South African hominin fossils could be placed into three distinct sub-families of South African "proto-men". These subfamilies consisted of Australopithecinae (Australopithecus africanus, Plesianthropus transvaalensis), Paranthropinae (Paranthropus robusts, Paranthropus crassidens) and Archanthropinae (Australopithecus prometheus, Telanthropus capensis). For those of you familiar with the hominin fossil record and hominin phylogentics you'll  note that only two (maybe three) of these species are considered valid taxa today.

In 1955 long-time friend and colleague of Broom, Raymond Dart, suggested that Broom had developed a habit of naming new hominin species every time he discovered a new fossil. Dart (1955) noted that Telanthropus capensis was remarkably similar to Pithecanthropus and Sinanthropus and that all three could be placed into the Archanthropinae sub-family. Following this, Simonetta (1957) moved Telanthropus capensis into the Pithecanthropus genus, renaming it Pithecanthropus capensis. Although Broom did not like this revision, Robinson agreed with the change. Following the taxonomic revisions of Homo erectus by Ernest Mayr (discussed previously in the first episode of Sunken Taxa), Robinson (1961) referred to the Telanthropus jaw as a South African representative of Homo erectus.

Today, there exists a difference of opinion among paleoanthropologists as to whether the African representatives of Homo erectus represent a distinct species from the Homo erectus specimens of Eurasia. Those who inclined to see the African population as distinct species include the Telanthropus jaw in the Homo ergaster hypodigm, making it the first Homo ergaster fossil ever discovered.

Monday, February 29, 2016

Miocene Monday Primate: Pliopithecus vindobonensis

From Zapfe (1958)
The majority of fossils attributed to the primate family Pliopithecoidea consist of isolated teeth and fragmentary maxillae and mandibles. Thankfully, for at least one species, Pliopithecus vindobonesis, there exists cranial and post-cranial fossils. These fossils give us a lot information, not just about one particular species, but about the pliopithecoid family as a whole.

The crania of P. vindobonesis shows us pliopithecoids had a relatively large and globular braincase and a projecting snout. The snout projects less than the propliopithecoids of North Africa (Aegyptopithecus), suggesting some prognathic reduction from the inferred common ancestor of these two primate families. The orbits are widely spaced and the mandible is long and robust, with a relatively broad ramus. Most importantly, however, the crania of P. vindobonensis, shows us that pliopithecoids had an incompletely ossified ectotympanic tube. This anatomical feature represents an intermediate stage between what is found in Platyrrhines (New World Monkeys), which do not have an ossified ectotympanic tube, and Catarrhines (Apes and Old World Monkeys), which have a completely ossified ectoympanic tube.
Edited from Begun (2002)
The skeleton of P. vindobonesis shows us that post-cranially pliopithecoids had an interesting mix of platyrrhine and catarrhine traits. The brachial index of P. vindobonesis (length of radius divided by the length of the humerus) is similar to that of a howler monkey, but the crural index (length of the tibia divided by the length of the femur) is similar to that of a gibbon. Proportionally, however, the forelimbs of vindobonesis were shorter than their hindlimbs, making them comparable to a baboon. The hands and feet of P. vindobonesis were long and curved suggesting that Pliopithecoids were adept and agile climbers. The post-crania of P. vindobonesis also shows that Pliopithecoids had an entepicondylar foramen, which is a primitive trait not found in any other catarrhine primates (extant or extinct). Finally, the fossils of P. vindobonesis show us, that unlike apes, Pliopithecoids retained their tails.

The fossils which represent Pliopithecus vindobonesis are perhaps the most important pliopithecoid specimens ever found. What little other Pliopitheocoid cranial and post-cranial fossils have been discovered suggest that this family was fairly morphologically uniform. I have an urge to resist the battle cry of paleoanthropology (i.e. "We need more fossils!"), but the fact remains, without additional postcranial pliopithecoid fossils we won't know if the body of P. vindobonesis was representative of most pliopithecoids, or whether it may be distinct in possessing this unique mix of primitive and derived catarrhine traits.

Wednesday, February 24, 2016

Sunken taxa: Ramapithecus, Bramapithecus, and Sugrivapithecus

I was originally planning to write about the rise and fall of the taxon Ramapithecus, but I realized I've already written a lengthy blog post about that back in 2011. Judging from the looks of what I wrote (shudder), I think the post originated from some sort of undergrad assignment.

The short version of the Ramapithecus story goes like this: Dr. Guy Pilgrim found some ape fossils in the Siwalik Hills (Pakistan, India, and Nepal) in the early 1900s. In 1910 he published a paper describing these specimens and erecting a number of new species. Some of these species were placed within the pre-existing Dryopithecus genus, but Pilgrim placed others into his newly created Sivapithecus genus.  Then, in the 1930s a paleoanthropologist named G.E. Lewis came along and took another look at the Siwalik fossils. He decided they were too different from the Dryopithecus fossils of Europe to be placed within the same genus, but also felt they all wouldn't fit into the Sivapithecus genus either.

In 1934 Lewis published an article in which he erected a number of new genera to accommodate the Siwalik fossils. The most important of these newly revised taxa was Ramapithecus. On the basis having a anteroposteriorly shortened canines and a parabolic dental arcade, Lewis suggested Ramapithecus was ancestral to modern humans.  This claim was largely ignored until it was picked up by David Pilbeam and Elwyn Simons in the 1960s. For more precise details of what happened next you can read my 2011 blog post. Suffice to say, subsequent field work in the Siwalik Hills resulted in the discovery of additional fossils, and eventually it was shown that Ramapithecus was not a distinct species, but a female Sivapithecus. As the Sivapithecus was named first, the Ramapithecus fossils were synonymized with Sivapithecus, and the taxonomic label Ramapithecus was sunk. Later studies eventually demonstrated that Sivapithecus was actually part of the Ponginae clade, making it more closely related to orangutans than it is to Hominae (gorillas, chimpanzees, and humans).

Bramapithecus punjabicus
Essentially,  Ramapithecus represents a textbook case of a sunken taxon, but still there's another part of this story that often goes ignored. Lewis (1934) also named two other genera in his publication: Bramapithecus and Sugrivapithecus.

Bramapithecus was the first of these two taxa to be sunk. It occurred when Simons (1964) began to review the Siwalik fossils and G.E. Lewis's descriptions. He realized all the Ramapithecus specimens consisted of upper teeth and all the Bramapithecus specimens were lower teeth. Simons put the teeth together and realized they fit perfectly. Thus, sunk Bramapithecus.

Similarly, Sugrivapithecus was also sunken by Simons and Pilbeam (1965). Well kinda.... See, Sugrivapithecus was only ever represented by a single fossil, which Lewis referred to as Sugrivapithecus salmontanus. Simons and Pilbeam argued that this fossil was really quite similar to Sivapithecus sivalensis and it could be lumped in there. At the time, however, Simons and Pilbeam had a habit of lumping most Miocene apes into Dryopithecus, so they originally referred to this species as Dryopithecus sivalensis. It was actually Prasad et al. (1969) who began referring to this specimen as Sivapithecus sivalensis.

By the mid-1980s Ramapithecus, Bramapithecus, and Sugrivapithecus had fallen out of usage. Today, nearly all paleoanthropologists recognize these three genera as really being part of the Sivapithecus genus.

Tuesday, February 23, 2016

Justin Bieber: professional primatologist

I know very little about the music of Justin Bieber. As I am a thirty-five year old man it's probably safe to say I'm not exactly his target market. Other than that time he appeared on Saturday Night Live and I changed the channel I haven't really been to exposed to his music. Still, I know enough to know that I don't like it. The little I've gleaned about his personality leads me to the belief that he's little more than a classic example of what happens when you give a spoiled child everything he wants. He takes it, expects more, and becomes confused and angry when he doesn't get his way.

Cool guy Bieber with his captive
victim, a white-headed capuchin
monkey (Cebus capucinus).
A few years ago Bieber was forced to leave his pet monkey in Germany. This is because Germany has laws which prevent assholes from using their airports to illegally transport exotic animals. This made out Bieber kinda sad, but he quickly got over it and left his monkey stranded in Germany while he continued to gallivant around the world singing love songs to prepubescent girls.

Once the world started to grow tired of Bieber's music and personality he hired a professional image consultant and tricked everyone into loving his over-privileged personality once again. And it's been working... at least that's what I read in Vanity Fair. Apparently, he sang a song on the Grammys and now we're suppose to love him again (The Grammys is that weird show where TV executives turn music into a competitive sport and rich people show up to give each other golden statues of antiquated stereo equipment).

That's all fine. Typically, I couldn't care less about the singing and dancing routine of commercial child star. Like I said, I'm not the target demographic, and I'm not one to put down the musical tastes of children. But I am one to put down idiots that endanger the lives of primates.

Justin Bieber is now planning to adopt another monkey. A number of animal rights groups are asking him to reconsider. Perhaps you think that's what I'm about to do, but I'm not. I'd like Justin to adopt a primate, but this time don't make it something cute like a capuchin monkey. This time I'd like to see him adopt an adult male chimpanzee. I'd also like to suggest that this chimp be allowed to live alongside Justin in his house. I think it's also a good idea if Justin teased the chimp and learned how to properly show signs of aggression and dominance. Then I'd like to see what is left of Justin after this chimp breaks his jaw, chews off his hands, and rips off his genitals. I think this could serve as a great learning opportunity to show the public that adopting primates as pets is juvenile and it could leave you disemboweled, disfigured, or dead. 

Monday, February 22, 2016

Miocene Monday Primate: Egarapithecus narcisoi

Egarapithecus narcisoi (Moyà-Solà et al., 2001)

Egarapithecus narcisoi was a pliopithecoid that inhabited Spain approximately 9 million years ago, making it the last known European pliopithecoid. Although little is known about its body proportions, it has been estimated to be about 10 kg, roughly the same size as a howler monkey. As with most pliopithecoids, Egarapithecus known solely by teeth and some small cranial fragments (partial maxilla and mandible). Still, the teeth have been very useful in showing that this species was highly derived compared to the other pliopithecoids. Egarapithecus has a unique combination of molar and premolar characters not found in other Pliopithecoids. These include unique traits like the tuberculum sextum of the lower third molar (an extreme accessory cusp found on the distal portion of the tooth).

Although the precise phylogenetic position of most pliopithecoids are not yet resolved, species are typically placed into one of three subfamilies: Dionysopithecinae, Pliopithecinae, and Crouzeliinae. In a cladistic analysis conducted by Moyà-Solà et al. (2001)), it was shown that Egararpithecus fits within the Crouzeliinae subfamily and forms a sister taxa relationship with Anapithecus hernyaki. Although this wasn't the most robust analysis, given the scarcity of comparative materials available, the other most parsimonious cladograms produced by Moyà-Solà and colleagues also suggested a strong relationship between Egarapithecus and Anapithecus. This prompted Alba & Moyà-Solà (2012) to suggest that the Crouzeliinae subfamily is composed of two tribes:  Crouzeliini and Anapithecini. Crouzeliini includes one genus, Pleisopliopithecus (with four distinct species), whereas Anapithecini contains four genera: Anapithecus, Laccopithecus, Barberapithecus, and Egarapithecus (each genus being composed of a single species).

Given that Egarapithecus is the last remaining European pliopithecoid, and it has such highly derived dentition, it raises the question as to whether it may have been too specialized. By too specialized I am suggesting that it may have had a very strict diet, and it is possible that it was not able to adapt to the cooling climate and changing vegetation of the late European Miocene. Of course, this is just speculation on my behalf. Still, we begin to see some changes in the faunal makeup of Europe around 8 million years ago, so it's not that crazy to suggest that the extinction of Egarapithecus may be in part linked to climate change.