Why did Fanged Cats have Long Forelimbs and Sloping Backs?

Until about 13,000 calender years ago, two species of large, powerful, fanged cats stalked the beautiful forests and plains of southeastern North America.

Smilodon depicted in top illustration; Dinobastis on the bottom.

The more famous saber-tooth (Smilodon fatalis) is well known from the thousands of specimens found in the La brae tar pits in California, but many have also been discovered in Florida, and some fossils of them have turned up in Alabama, Tennessee, and South Carolina.  Fossils of the scimitar-tooth (Dinobastis serus) are less common–nearly complete skeletons in North America only being discovered in Friesenhahn Cave, Bexar County, Texas, though individual specimens have been found in Oklahoma, Tennessee, Florida, and some western states, such as Alaska.  This latter species had a worldwide distribution, leaving fossils in what today is England as well as Africa.

Sketch of skull found in Friesenhahn Cave from The Bulletin of the Texas Memorial Museum number 2 September 1961.

The skulls of both species of fanged cats are similar, but the two differ greatly in dentition.  The scimitar-tooth had larger incisors, but its fangs or canines were shorter and smaller.  Smilodon’s fangs were serrated in front; Dinobastis’s were serrated on both sides. When Smilodon closed its mouth, the fangs extended lower than the jaw, while Dinobastis’s fangs only reached the bottom of the jaw.

Both species had longer forelimbs than hindlimbs.  The scimitar-tooths had even longer forelimbs than the saber-tooth’s, but they weren’t quite as heavily built.

Based on anatomical characteristics, scientists believed saber-tooths and scimitar-tooths were closely related, and a recent study of DNA supports this hypothesis.  They are considered a sub-family within the Felidae.  The fanged cats are in the Machairodontinae, while all other cats, including every extant species, are considered to be in the Felinae.  See: http://www.adelaide.edu.au/acad/publications/papers/SmilodonFinal.pdf

The fanged cats had a sloping back, much like modern day hyenas (Crocuta crocuta), and likely ran about in a gait that would have resembled that of a hyena.  I’ve often wondered why they were built like this.  Some scientists speculate the longer forelimbs gave them an advantage when hunting juvenile proboscideans.  But it occurred to me after watching videos of a hyena fighting off a pack of wild African hunting dogs, that perhaps this build made it easier for them to do battle with packs of wild canids, such as their most important ecological competitor, the dire wolf, though dholes or red Indian dogs also occurred in the central part of North America during the Pleistocene, and were probably an important competitor there as well.

http://www.youtube.com/watch?v=YiqAxa1tJ5g

Perhaps with a sloping back, it was easier for the fanged cats to sit on their haunches and use their paws and fangs to defend themselves against packs of wolves that would’ve tried to nip them from behind and even bite their hamstrings.

Cats are distantly related to hyenas.  The cat branch on the evolutionary tree is placed next to the hyena branch, and the machairodontinae sub-family is the closest cat related to the hyenas.  The trait of a sloping back and longer forelimbs evolved millions of years before the Pleistocene, perhaps originating with some common ancestor of hyenas and cats.

Friesenhahn Cave in Bexar County, Texas

This is a really nice sketch of Friesenhahn Cave from the previously mentioned periodical.  The artist’s name isn’t given.

A sinkhole on a cattle ranch in south central Texas opens to an ancient cave where thousands of Pleistocene age fossils have been preserved.  Two nearly complete skeletons of the scimitar cat were discovered here about fifty years ago, along with the skeletons of two scimitar cat kittens.  This species periodically must have used the cave as a den for millennia.  The Pleistocene-age fossils are dated from between 19,000-17,000 years BP.  Some other fossils in the cave date to 9,000 BP, and some are even more recent, dating to less than 300 years BP.   Scientists believe the surrounding environment was mostly arid grassland, but occasional heavy rains (due to the drastically fluctuating Ice Age climate) caused flash floods that washed sediment into the cave, burying the bones of dead animals.  Later, the cave entrance collapsed, sealing the bones from the atmosphere.  Moreover, the limestone in the soil contributed to the preservation of the fossil material.  The sinkhole formed recently, providing the opportunity for people to discover the cave.

Thousands of baby mammoth teeth were recovered here–evidence that scimitar cats ambushed them and dragged them in the cave.  Though a pond that existed in the cave may have attracted herbivores seeking drinking water, the sheer number of individual baby mammoth specimens that accumulated here must have been the result of scimitar-tooth cat predation.  Scimitar-tooth cats must have specialized in preying on juvenile proboscideans–baby mastodon teeth were found here too.  How they successfully hunted baby mammoths, guarded by adults, is a mystery.  I assume they ambushed ones that wondered too far from the herd.

In addition to the scimitar cat fossils, the cave was the final resting place for many other Pleistocene animals.  One tooth of the other fanged cat, Smilodon fatalis, was found here along with many coyote fossils, and some of black bear.  Other remains include mammoth, mastodon, ground sloth, deer, bison, horse, camel, tapir, long-nosed peccary (a nearly complete skeleton), flat-headed peccary, black-tailed jack rabbit, cottontail rabbit, eastern chipmunk, pocket gopher, bog lemming, pine vole, eastern mole, short-tailed shrew, desert shrew, giant tortoise, box turtle, aquatic turtles, toads, snakes, and lizards.  There may be some human artificats, but nothing definite because it’s sometimes difficult to distinguish natural artifacts from manmade ones.

Scientists think the Pleistocene environment that existed at the time the specimens were deposed is one that no longer occurs anywhere.  They believe that what was to become Bexar County was mostly an arid grassland interspersed with riparian woodlands consisting of deciduous trees.  It is strange that the desert shrew, a species of the southwest desert, lived near the eastern chipmunk which lives in moist woodlands.  And indeed grassland species (bison, horse, camel, mammoth) and woodland species (mastodon, deer, long-nosed peccary, tapir) both found suitable habitat near the cave.

 

Advertisements

Tags: , , , , , , , , , ,

3 Responses to “Why did Fanged Cats have Long Forelimbs and Sloping Backs?”

  1. Bruce Keegan Says:

    An excellent article.
    As at La Brea, animals that are forest dwellers, Mastodon) and grassland species, (Mammoths) indicate climate changes at this location over the period of 19,000 yrs BP to the present. What does carbon dateing show ?

  2. Big Cats Hunting Elephants « GeorgiaBeforePeople Says:

    […] found in Friesenhahn Cave, Texas associated with fossil skeletons of the scimitar-toothed cat.  (https://markgelbart.wordpress.com/2010/10/08/why-did-fanged-cats-have-long-forelimbs-and-sloping-bac… )   Gnaw marks on the long bones of the proboscideans match those from the teeth of this cat.  […]

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s


%d bloggers like this: