Two Pleistocene Carnivore Dens Near Miami, Florida (Part 2)

Scientists unearthed thousands of bones from the Cutler Hammock site during the mid-1980’s.  The fossils were identified, catalogued, and sent to the University of Florida Museum.  Many of the specimens remain unstudied in detail, and this rich assortment offers an opportunity for paleontologists looking for research material.  The site itself was not completely excavated and is potentially available for future study.  Originally, it was a cone-shaped sinkhole cave filled with sediment, rocks, and fossils. The lower half was below the water table.  The suface was 5 meters by 6 meters wide and from 3 meters to 5 meters deep in various places.  Workers bulldozed sand over the unexcavated section, making it easy for future scientists to re-dig but protecting it from unauthorized fossil hunters.    It’s located on land that is part of Deering Estate Park–a protected environmental, historical, and archaeological preserve of 444 acres in extent.  The preserve is a rare natural area within the suburban sprawl of Miami, Florida and includes endangered pine rocklands, tropical hardwood hammock, mangrove woods, and salt marsh.

The Deering Estate.  Deering was an industrialist who decided to protect his estate from development in perpetuity.  The Cutler Hammock fossil site is located on this property.

Gary Morgan and Steve Emslie studied many of the large vertebrate bones found at Cutler Hammock, and they wrote the paper from which I mined most of the information I used for this blog entry.  They noticed a high number of bones here had gnaw marks on them and concluded this former cave served as a carnivore den during the Pleistocene.  The most common large carnivore fossils found at this site were from dire wolves (Canis dirus), totaling 42 individuals.  This is the third largest dire wolf assemblage in the world behind the La Brea Tar Pits and San Josecito Cave in Mexico.  They also found bones from 9 spectacled bears (the extinct Tremarctos floridanus), 5 coyotes (Canis latrans), 4 jaguars (Panthera onca), 3 bobcats (Lynx rufus), 1 sabertooth (Smilodon fatalis), 1 American lion (Panthera atrox), 1 cougar (Puma concolor), and 1 black bear (Ursus americanus).   The authors of the study suggest the cave was a rendezvous site for packs of dire wolves and not a place where pups were birthed.  They speculate the cave was near a source of water that attracted various prey species.  In another paper Gary Morgan mentioned that the coyote fossils found at Cutler Hammock were unusually small.  Some think they may actually belong to dogs (Canis familiaris) brought by man.  If so, it’s possible the bones may be from yellow dogs, the American dingos, which readily revert to the wild state and are capable of surviving without humans.

direwolfmorphology

Photos of deer and peccary bones gnawed by dire wolves at the Cutler Hammock site.  Click to enlarge. From the below referenced paper.

direwolfmorphology 001

Photo of dire wolf lower jaw and dire wolf teeth found at the Cutler Hammock site.  Click to enlarge.  Also from the below referenced paper.

Most of the bones from prey species have puncture marks–a telltale characteristic of canid gnawing.  The extinct long-nosed peccary (Mylohyus nasatus) was the most common victim of dire wolves, numbering 75 individuals of which one-third were juveniles.  Horses were the next most common dire wolf victim, though 17 of the 19 individuals were juveniles.  Next in descending order of abundance were white-tailed deer, bison, llamas, and 1 mammoth that was probably scavenged.

Tremarctos floridanus was a close relative of the extant spectacled bear (Tremarctos ornatus) of South America.  Spectacled bears are primarily vegetarian but occasionally eat meat.  Bones scavenged by bears show recognizable differences from bones scavenged by canids.  None of the Cutler Hammock bones show evidence of bear gnawing.  (Hint to professional paleontologists: the authors of this study didn’t examine the bones for evidence of big cat gnawing.  It’s a potential topic for future research.)  Scientists also found bones from mastodon, Harlan’s ground sloth, and the pampathere (a 300 pound grass-eating armadillo) at Cutler Hammock but these showed no evidence of being gnawed upon.

A hearth and bones from 3 adult and 2 juvenile humans (Homo sapiens) were found just above the level where Pleistocene fossils were found.  This material dates to ~11,100 calender years BP.  A human bone found associated with dire wolf bones (in situ) was found as well.  The radiocarbon dating on this bone is considered unreliable.  It’s possible this human bone is as old as the dire wolf bones.  However, there has been much bioturbation at this site.  Land crabs dig holes in this locality, and their actions can mix bones of different ages together.  Or humans may have buried the corpse into the fossil deposit.  Nevertheless, this human bone has dire wolf gnawmarks on it–evidence this person was scavenged (or even killed) by dire wolves.

The below referenced article lists all the vertebrate species identified from Cutler Hammock, and as I read through the list, I noticed a few interesting bird species I neglected to mention in my discussion from part 1 of this blog entry.  The extinct hawk-eagle (Spizaetus grinnelli) flew the skies of Pleistocene south Florida.  It was larger than its closest living relative, Spizaetus ornata.

Spizaetus ornatus

South American hawk-eagle.  It some times takes prey 5 times its size.  A bird like this lived in Ice Age Florida.

An extinct species of caracara (Milvago reidei), closely related to the living yellow crested caracara, also of South America, lived on the open plains of Florida then.  Passenger pigeons (Ectopistes migratorius) must have occasionally darkened the skies.

The Monkey Jungle Hammock site is thought to have been a carnivore den site as well but as far as I know no study has been conducted on the morphology of bones found there (Another hint to paleontologists.)

Reference:

Emslie, Steve; and Gary Morgan

“Taphonomy of a Late Pleistocene Carnivore Den in Dade County, Florida”

Late Quaternary Environments and Deep History: Tributes to the Career of Paul Martin

Edited by David Steadman and Jim Mead

Hot Springs South Dakota Inc. Reasearch Papers Volume 3 1995

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