Tremarctos floridanus

Tremarctos floridanus is called the Florida spectacled bear, Florida cave bear, or rarely Florida short-faced bear. Originally, James W. Gidley named this animal Arctodus floridanus in 1928, until affinities with the spectacled bear were realised by Chester Stock when specimens from San Josecito Cave were recovered in 1950. Described as Tremarctos mexicanus, it was recombined as T. floridanus by Björn Kurtén (1963), and Kurtén and Anderson (1980). Despite at least 35 individuals being recovered by 1967, almost all specimens consist of isolated teeth & skull fragments, save for the type specimen (from the Golf Course site of the Melbourne Bone Bed in Melbourne, Florida). Despite one such common name, T. floridanus is not considered a close relative of the Eurasian cave bear (Ursus spelaeus), which belonged to a different genus and subfamily. the proportions of the humerus, femur and neck in particular are longer than T. ornatus, with T. floridanus being described as a relatively long-limbed species. Additionally, while the forelimbs are longer than the hindlimbs in T. ornatus (likely due to arboreal activity), they are of equal length in T. floridanus. However, the paws of T. floridanus are proportionally shorter and smaller than T. ornatus. while T. ornatus does not. The lower jaws of T. floridanus are larger; while the ramus of the mandible is taller in T. floridanus, the relative height of the mandible's coronoid process is the same in both species. Meanwhile, the M2 of Arctodus is broader and more robust than Tremarctos. In addition to general cranial and dental differences between tremarctine and ursine bears, T. floridanus can also be distinguished from American black bears via their postcranial skeletons. The forelimbs of T. floridanus evidenced an entepicondylar foramen on the humerus, with the proximal end of the radius in T. floridanus being oval-shaped (while this is triangle-shaped in the American black bear). The cervical vertebrae are divergent in the orientation, form and proportions, while the number of ribs (13 sets in T. floridanus, 14 in the American black bear) is also different. The ischial bar and bone ridge of the acetabulum in the pelvis of T. floridanus are more narrow, while the greater trochanter is taller in the femur of T. floridanus. == Evolution ==

The closest living relative of the T. floridanus is the spectacled bear (T. ornatus) of South America; they are classified together with other short-faced bears (Arctodus, Arctotherium, Plionarctos) in the subfamily Tremarctinae. Tremarctine bears first appear as Plionarctos during the late Miocene epoch of North America. An investigation into the mitochondrial DNA of bear species indicates that short-faced bears diverged from the Ursinae subfamily approximately 5.7 million years ago. Around the Miocene-Pliocene boundary (~5.3Ma), tremarctine bears, along with other ursids, experienced an explosive radiation in diversity, as C4 vegetation (grasses) and open habitats dominated. The world experienced a major temperature drop and increased seasonality, and a faunal turnover which extinguished 70–80% of North American genera. Correspondingly, the genetic divergence date for Arctodus is between 5.5 million and 4.8 million years ago, All three genera evolved from Plionarctos in the Blancan faunal stage of North America, and are first recorded as the medium-sized Arctodus pristinus, Tremarctos floridanus and Arctotherium sp. from the Late Blancan (Late Pliocene / Early Pleistocene) of North America circa 2.6 million years ago. The Intermontane Plateaus preserve the oldest possible remains of T. floridanus, being from Palm Spring Formation (Anza-Borrego, California, ~2.7Ma), and San Simon (Arizona ca. 2.2Ma), although the Grand View specimen may instead represent Plionarctos. researchers suggest that indeterminate ursid from the mid-Blancan Buckhorn fauna (New Mexico, 4Ma - 3Ma) may represent either Tremarctos sp. or Protarctos abtrusus. Unlike its Neotropical sister species (T. ornatus), T. floridanus was a temperate species that has almost entirely been recovered from Nearctic sites. The fossil record of T. ornatus is unknown, as T. ornatus remains do not appear in the South American record until the Holocene, which may indicate that T. ornatus emerged from T. floridanus in the Holocene. Genetic research on the mitochondrial DNA of tremarctine bears indicates Tremarctos was more closely related to Arctotherium than Arctodus. However, a preliminary investigation of tremarctine bear's nuclear DNA suggests an extensive history of hybridization between Tremarctos and Arctodus in North America, although hybridization with Arctotherium (likely A. wingei) as the Tremarctos genus migrated southwards into South America is also possible. Evidence of gene flow between Tremarctos and an ursine bear was also uncovered, most likely due to the extensive overlap between Tremarctos and the ancestors of the American black bear in Pleistocene North America. ==Description==

'', its surviving sister species. Skull The canalis semicircularis lateral suggests that T. floridanus had a head posture of 38°, which is more oblique than its sister species T. ornatus (29°); as T. ornatus inhabits densely vegetated areas, the more oblique head posture in T. floridanus could infer a greater capacity for long distance vision. Tremarctos floridanus has mandibular condyles raised well above the plane of the teeth, As in other tremarctine bears, tooth size (particularly the P4) could be variable, as exemplified by an average sized female from Tennessee possessing the largest known teeth in T. floridanus, with some even comparable to Arctodus. Like other tremarctine bears, T. floridanus was highly sexually dimorphic, Like T. ornatus and A. simus, T. floridanus possessed a false thumb. ==Range==

Blancan and Irvingtonian The distribution of Tremarctos floridanus changed across its natural history. In the Blancan (4.75Ma to 1.806Ma) and Irvingtonian (1.806Ma to 250,000 BP) faunal stages, T. floridanus remains are sparse, and solely recovered from western North America. with the Anza-Borrego Desert in California recording both Late Blancan and Irvingtonian remains. T. floridanus was recorded from the Blancan Hagerman Fossil Beds, but these have been reassigned to Protarctos abstrusus. but subsequent research establishes Arctodus pristinus was the only tremarctine bear present at the locality. Rancholabrean may have limited the distribution of T. floridanus in southern Mexico and Central America.'' However, in the proceeding Rancholabrean epoch (250,000 BP to 11,700 BP), T. floridanus was widely distributed along the eastern Atlantic Plain and the broader Gulf Coast. Fossils have been recovered from the US states of Florida, Georgia, South Carolina, Tennessee, and the Mexican states of Michoacán, and Nuevo León. T. floridanus is suggested to have expanded its range into higher altitudes during warmer interstadials and interglacials, which would explain its presence in Inner Space Cavern on Edwards Plateau, Texas. The Grassy Cove Saltpeter Cave specimen, from Cumberland Plateau, Tennessee, has been radiocarbon dated to within the climatically unstable MIS 3. T. floridanus has been described from Belize, however the recent reassignment of a T. floridanus specimen to the morphologically similar Arctotherium wingei from the Hoyo Negro, and other positive identifications of A. wingei from Belize have put under question current T. floridanus identifications in Yucatán Peninsula. Current scholarly analysis asserts that A. wingei may have restricted the range of T. floridanus outside of Central & South America until the extinction of A. wingei, where subsequently Tremarctos begins to be found in the South America. Additionally, T. floridanus specimens assigned by Kurtén in New Mexico (such as Isleta Caves and Conkling Cavern) have been reassigned to Arctodus simus - no western specimens of T. floridanus have been found in the Rancholabrean. Map of fossil localities == Paleoecology ==

Atlantic Plain may have been a competitor of its fellow Tremarctine relative Tremarctos floridanus'' in the Atlantic Plain. The Atlantic Plain (in particular Florida) hosts the greatest number of T. floridanus specimens on the continent, coming from well known sites such as Aucilla River, Cutler Fossil Site, Devil's Den Cave, Haile Quarry site, Melbourne Bone Bed, Rock Springs and Vero Beach. Generally speaking, large tremarctine fossils from the Early and Middle Pleistocene of Florida are considered to be A. pristinus, whereas those from the Late Pleistocene of Florida are considered to be T. floridanus. Indeed, black bears and Tremarctos floridanus are believed to have only colonized Florida with the extinction of A. pristinus (both of which only appear in Florida in the Late Pleistocene), however, T. floridanus could yet still be found from older sites in Florida. At the Rainbow River and Lake Rousseau localities in Rancholabrean Florida, Tremarctos floridanus have been recovered alongside Smilodon, dire wolves, jaguars, ground sloths (Megalonyx, Paramylodon), llamas (Hemiauchenia, Palaeolama), Vero's tapir, giant beaver, capybara, Holmesina, horses, Bison antiquus, mastodon, Columbian mammoths and Arctodus simus, in a climate similar to today's. Furthermore, the abundance of black bears, and particularly Tremarctos floridanus in Florida, has led to a theorized niche partitioning of ursids in Florida, with Tremarctos floridanus being herbivorous, and black bears and Arctodus simus being omnivorous, with Arctodus being possibly more inclined towards carnivory. During the Rancholabrean, Florida and the Gulf Coast hosted a subtropical faunal region. Sometimes referred to as the Holmesina ("Chlamytherium") -glyptodont faunal province, T. floridanus was joined by other key indicator species such as Holmesina, Glyptotherium, capybaras, Eremotherium, Cuvieronius, Hesperotestudo, Mylohyus, Palaeolama, and Dasypus bellus. The now submerged continental shelf in the Gulf of Mexico appears to have provided a dispersal corridor consisting of savanna and thorn scrub habitats between south Texas and Florida for these largely Neotropical fauna. Appalachian Highlands specimen from Tennessee is the northernmost confirmed individual of T. floridanus yet recovered. The Grassy Cove Saltpeter Cave specimen was radiocarbon dated to 33,660 ± 3980 radiocarbon BP. An isotope study on a T. floridanus individual from Ladd's Quarry, Georgia broadly reconstructed the specimen as an omnivore. Interior Plains Laubach III in the Inner Space Cavern (dated to ca. 23,230 ± 490 radiocarbon BP) of the Interior Plains contains many animals that have modern relatives associated with subtropical climates, including Tremarctos floridanus, common opossum, Mexican free-tailed bat, jaguar, armadillo, and Glyptotherium. The fauna appears to have been deposited under a generally warm climate (inter-stadial). Interactions with humans Several Rancholabrean localities in Florida have recovered both T. floridanus and humans from identical strata (Devil's Den Cave, Melbourne Bone Bed, Vero Beach), indicating a co-existence during the terminal Pleistocene. While the remains at Devil's Den Cave were once dated to 8,000 BP, == Extinction ==

by the Florida Geological Survey (1959). The chronology of megafaunal extinctions (such as Tremarctos floridanus) in the Late Pleistocene extinctions has been disputed. The last reliable direct radiocarbon date for T. floridanus is 23,230 ± 490 BP, from Laubach Cave No. III, Texas. In the United States, T. floridanus remains from the end of the Pleistocene are concentrated in the Atlantic Plains, having been recovered from 15 localities; this is in contrast with the Interior Plains (one locality) and Appalachian Highlands (two localities). Molecular evidence from Colombian, Ecuadorian and Venezuelan T. ornatus specimens suggests an internal population divergence occurred between 15,000 and 25,000 thousand years ago, ==References==