artiodactyl

2

Indohyus

Reconstruction by Carl Buell.

When: Eocene (~48 million years old)

Where: India and Pakistan

What: Indohyus is a fossil artiodactyl that falls on the lineage leading to whales. The discovery of an almost complete specimen Indohyus helped to answer one of the long standing questions in the early evolution of whales. All living whales are carnivorous (with diets ranging from vertebrate prey to tiny invertebrates), however, all other living artiodactyls are predominately herbivorous. As all fossils assuredly related to whales showed both aquatic and carnivorous adaptations, it was a mystery as to which came first in the evolution of the cetaceans. Enter Indohyus. This fossil lacks any carnivorous adaptions in its dentition, but has several adaptations for spending time submerged - most notable are an ear region that looks a lot like that of previously known fossil whale ancestors and bones with increased density. These features would have allowed the animal to hear better underwater and to stay submerged easier, respectively. Isotopic analysis of its dentition and bones suggests that Indohyus spent a good amount of time in waters, but fed on land plants - much like the modern Hippopotomus. It has been suggested Indohyus fled to the water to avoid predators, like the modern African Mousedeer, which has been documented spending almost five minutes underwater to escape predation. Indohyus  was about 3 feet (~1 meter) long from end to end, thus it would have had many potential predators in the early Eocene world. 

Phylogenetic analysis place Indohyus at the base of what have traditionally been referred to as ‘archaeocetes’; a paraphyletic lineage of fossils more closely related to whales than to hippos. The term Cetaceamorpha is used for the group that includes all living whales and all fossils more closely related to them than to the hippos. Falling very near Indohyus is an animal called Diacodexis. I will highlight this animal more in a future entry, but to be brief it shows none of the aquatic adaptions of Indohyus, but has simular dentition. Thus, the current hypothesis of basal whale evolution is that small deer-like animals first went into the water, possibly for protection from predators, and then later became carnivorous. 

2

Andrewsarchus mongoliensis (“Andrew’s Ruler”)

….One of my favorite prehistoric mammals for semi-obvious reasons, Andrewsarchus was a species of mammal that lived during the Eocene epoch. Although Andrewsarchus looks similar to a creodont or carnivoran it is actually more closely related to Artiodactyls.

A.mongoliensis is known only from a single meter long skull found in Mongolia and as such much of its paleobiology is up for debate. Some sources claim it could of been a predator and others claim it was a scavenger. Newer theories claim that it could of been an omnivore due to its ‘blunt’ teeth. However, Andrewsarchus did posses a very strong set of jaws, one of the strongest of all land mammals, and could bite straight through bones. Judging from the coastal location of its fossil Andrewsarchus probably frequented beaches and likely fed beached whales, turtles, shellfish and large land mammals (such as brontotheres)

Phylogeny

Animalia-Chordata-Mammalia-Artiodactyla-Andrewsarchus-A.mongoliensis

Images: DiBgd and Ryan Somma

‘The phylogenetic position of Cetacea relative to other extant artiodactyls’

'Artwork is by Carl Buell. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)’

A phylogenetic blueprint for a modern whale. Gatesy J, Geisler JH, Chang J, Buell C, Berta A, Meredith RW, Springer MS, McGowen MR. Mol Phylogenet Evol. 2012 Oct 26. pii: S1055-7903(12)00418-6. doi: 10.1016/j.ympev.2012.10.012. (pdf)

6

Cervidae

I had a request yesterday from my follower mngwa to see the skull of a Chinese water deer (Hydropotes inermis) – unfortunately we don’t have one in our collection, but we do have the skull of a species of barking deer, also known as a Muntjac.  Our skull belongs to a Chinese barking deer, a.k.a. Reeves’s muntjac (Muntiacus reevesi). I hope it suffices!

 What is remarkable about all of these variable species is that they are all in the same family, Cervidae, the deer.  I posted some photos of an incredibly adorable young mule deer live-mount yesterday (Odocoileus hemionus), so today I thought I would include a North American moose (Alces alces) and a white-tailed deer (Odocoileus virginianus) skull to show morphological similarities and differences between the three species.  The size disparity between them is remarkable, not to mention the extreme variability in antler growth and shape (obviously, the antlers have been sawed off from the moose skull, but you can imagine).  Why do you think muntjacs have such extremely elongated canines?  And a trickier question I haven’t figured out yet – why do the pedicles (the fleshy part around the base of the antler where it is shed annually) start growth so far back from the base of the cranium?

3

Megaloceros - The Irish Elk or Giant Deer 

When: Mid Pleistocene to Early Holocene (400,000 to 8,000 years ago) 

Where: Throughout Eurasia, ranging from the British Isles to China.  

What: Megaloceros had the largest antlers of any known deer. It ranged all over Eurasia, with a vast quantity of fossils known from Irish peat bogs, giving it the common name of ‘The Irish Elk’. As Megaloceros is not an elk, but rather a 'true deer’ in the clade Cervini, the name 'Giant Deer’ is sometimes used instead, by people who really care about that sort of thing.  Megaloceros stood roughly 7 feet (~2 meters) tall at the shoulder, with antlers up to 12 feet (3.6 m) wide from tip to tip. 

These large antlers have received a lot of attention, for obvious reasons. They are thought to be only for display, as their orientations and placement upon the skull are far from ideal for use in fights between males for mates. The size of the antlers has been suggested to be the reason for the extinction of this deer in several different hypotheses, but none of them have stood up to strong scrutiny. Megaloceras is one of many fossil animals for which we have no clear explanation for its extinction. 

vine

This is not a dinosaur, but the way giraffes run is weird 

“A composite phylogenetic hypothesis for Artiodactyla, including Cetacea. The overall tree is the result of merging topologies derived from supermatrix analyses of three concatenated datasets that include molecular, phenotypic, and fossil information: Mysticeti (Deméré et al., 2008; this study), crown Cetacea (Geisler et al., 2011), and Artiodactyla (Geisler et al., 2007; Spaulding et al., 2009; this study). Thick branches connect extant taxa in the tree, and thin branches represent extinct lineages. Brackets to the right delimit clades and stem groups to crown clades; the small, inset tree delimits Cetacea (blue) and Artiodactyla (yellow). Approximate evolutionary time-scale, in millions of years, is at the base of the figure (see Section 2 for basis). For the mysticete section of the composite tree, one of the six minimum length trees derived from the Mysticeti supermatrix is shown here. Relationships derived from the Artiodactyla supermatrix (stem Cetacea, basal artiodactyl relationships, outgroups) and from the crown Cetacea supermatrix (Odontoceti) are based on strict consensus trees. Artwork is by Carl Buell. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)”

A phylogenetic blueprint for a modern whale. Gatesy J, Geisler JH, Chang J, Buell C, Berta A, Meredith RW, Springer MS, McGowen MR. Mol Phylogenet Evol. 2012 Oct 26. pii: S1055-7903(12)00418-6. doi: 10.1016/j.ympev.2012.10.012. (pdf)

2

Our exhibit, The Historical Collections of the Philip L. Wright Zoological Museum is opening this afternoon!  Come join us at 4pm on the first floor of Health Sciences for the dramatic unveiling – we’ll also have cookies and refreshments, including these ’gingerbear’ cookies with almond icing skeletons that I labored over last night.  My friend Hannah is a professional cupcake decorator, and I could have totally used her help because some turned out a little derpy, but I’m sure they’ll all taste the same. 

Check back tomorrow for pictures of our little reception, the exhibit, and the Freak of the Week!  CAN’T WAIT!

2

Shansitherium

When: Late Miocene (~ 11 - 6 Million years ago)

Where: China

What: Shansitherium is a fossil relative of the giraffe. Giraffes are a commonly used example of an easy to see evolutionary transformation, the neck getting longer and longer, and here is some of the evidence used to show that hypothesis. Shansitherium lived in the late Miocene of China, and falls closer to the giraffe line than any other extant clade of artiodactyls. It possesses horns like that of the modern giraffe and okapi, which probably would have been covered with skin in life (these are called ossicones), but over all looks much more like a moose than a giraffe. 

Today the Giraffidaehas only two living species, the giraffe (duh) and the okapi, and is only found in sub saharan-Africa. In the Miocene however this group was far more diverse, with Shansitherium just one example of the over a dozen species that roamed all over not just Africa, but Asia and Europe as well. The late Miocene was a time of cooling and drying climates in much of the world, and this is probably what lead to the reduction of species in this clade. 

Reconstruction by Willem van der Merwe.

4

Odocoileus hemionus 

I have to make up for the super nasty llama I posted yesterday, so instead I pulled down this beautiful baby mule deer (Odocoileus hemionus) which lives high on a shelf in the museum.  I’ve been itching to photograph it since I discovered it tucked away last semester.  If I could run off with any one specimen in the museum to put in my house and admire forever, it would probably be this adorable creature.  Ungulates and artiodactyls are arguably my favorite animals (but also mustelids, felids, canids, pinnipeds …. ) and I’ve always had a special place in my heart for deer.  Plus, look at this gorgeous baby!  My god, I can’t even handle it.  

Archaeotherium was a genus of artiodactyls in the family Entelodontidae of the suborder Suina, making them relatives of modern day pigs. Archaeotheres, unlike their better-known cousins, were predators. The bones of other mammals, including the jaws of rhinoceros ancestors, have been found with marks that match the fangs of these giant swines. Evidence also shows that, similar to leopards of today, they kept stashes of food hidden away from potential thieves. A fossil trackway even shows the tracks of a Subhyracodon stopping to see an Archaeothere approach, and then falling into a gallop with Archaeotherium’s tracks in pursuit. They had large neck muscles to support a heavy head, and large olfactory lobes which suggests they had a strong sense of smell. Large predators, they stood at about 1.2 meters at the shoulder and were 2 meters long. Despite being apex predators, it is believed that in times when prey was scarce, Archaeotherium would eat roots and tubers much like modern day pigs.

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Klipspringers.  I had to give a presentation on these cuties today.  I thought I’d share some facts, since I fell in love with them.  I am a zoology major, after all.

Scientific name: Oreotragus oreotragus

  • only gets to be 4 feet long and 2.5 feet at the shoulder
  • have hollow hair that grows on end, not laying flat to the body
  • The hooves are very small- the animal can stand all four feet on a silver dollar and each hoof has the diameter of a dime
  • stands on the very tip of the hoof, no other ungulate can claim this
  • large preorbital gland (black area in front of the eye) used to mark territories
  • small family groups of mated pair and offspring
  • monogamous
  • able to jump up a smooth flat wall
  • live in rocky areas with some brush
  • native to Africa