Extinct species of alligator
Alligator hailensis, or Haile alligator, is a large,
History and naming
The remains of Alligator hailensis were found in the Haile 7C and 7G fossil sites, late
Alachua County, Florida, likely representing water-filled sinkholes that were covered in sediments. These fossil localities yielded a minimum of forty-three individual alligators, possibly even more, bridging the gap between species from the Pliocene and the modern American alligator. Out of these, specimen UF 224688, a complete skull with mandible and assorted postcranial remains ranging from vertebrae to limb bones, was chosen as the
holotype. The
specific name hailensis is derived from the name of the fossil sites.
[1]Description
The Haile alligator was a large animal, comparable to the modern Mississippi alligator in size with the holotype skull measuring 52.5 cm (20.7 in) from the tip of the snout to the end of the parietal bone and 15 cm (5.9 in) across the widest point of the maxilla. A larger, tho less complete specimen even measures up to 20 cm (7.9 in) across the maxilla.[1] Using the dimensions of the holotype skull the larger specimen would have a skull length of 28 inches, if it had a skull to body length ratio similar to the modern day alligator (1:7.5),[3] the larger specimen would have a total length of 17.5 feet.
The nares of the animal are oval in shape and is almost split in two by the
supratemporal fenestrae are rounded, giving the parietal an hourglass shape. The axial and epaxial skeleton are largely similar to other species of alligators, however
Alligator hailensis stands out as being known from much more material than other extinct members of the genus across various age groups. Much like other alligators,
A. hailensis lacked osteoderms on its belly. The species differs from
A. mefferdi in the placement of the suture between
pterygoid and
palatine, which is situated before the rear edge of the suborbital fenestra. From the modern alligator it differs in the extent of the
splenial, which in
A. hailensis makes up around forty percent of the medial wall of the mandibular toothrow. Additionally, it differs from any other species of alligator through the presence of an anterior foramen intermandibularis oralis (a foramen located on the anterior end of the splenial) which is incompletely closed. In modern species, the
Chinese alligator possesses this foramen while the
American alligator lacks this feature.
[1]Evolution
Both in regards to morphology and chronology, the Haile alligator forms an intermediate form between American Midwest. Stout acknowledges that one could argue that the Haile alligator may represent a glimpse into the
anagenetic evolution of modern alligators, however maintains that the remains are morphologically distinct enough to warrant the creation of a functional species. The plurality consensus tree recovered by Stout is shown below.
[1]
Paleobiology
In addition to both cranial and postcranial remains, researchers also discovered multiple
coprolites (fossilized feces) at the Haile fossil site. These coprolites are consistent in shape with those of crocodilians and were thus assumed to be those of
Alligator hailensis. Encased in the fossil were remains identified to belong to fish, indicating that at least some part of the Haile alligator's diet consisted of fish.
[1]References
