| Barbclabornia | |
|---|---|
 | |
| Barbclabornia luedersensis teeth | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Chondrichthyes |
| Subclass: | Elasmobranchii |
| Infraclass: | †Xenacanthimorpha |
| Order: | †Bransonelliformes |
| Genus: | †Barbclabornia Johnson, 2003[2] |
| Species: | †B. luedersensis |
| Binomial name | |
| †Barbclabornia luedersensis Berman 1970[1] | |
| Synonyms[3] { | |
Barbclabornia is an extinctgenus ofxenacanth from the EarlyPermian and possibly upperPennsylvanian ofNorth America. The genus contains a single described species:B. luedersensis. It has been found in several places withinAsselian andAtinskian formations, including theClear Fork,Albany,Wichita, andDunkard Groups. There are possible examples from theGzhelian-agedAdmire,Monongahela, andConemaugh groups.[2][4]
Barbclabornia was initially only known from isolatedteeth, which were assigned to the genusXenacanthus in 1970 based on the belief that all UpperPaleozoic xenacanthids belonged to said genus. In 2003,X. luedersensis would be reassigned to a new genus after differences in tooth structure were described, and with the discovery of a largepalatoquadrate bearingluedersensis teeth atLake Frederick.[2][5]
The genusBarbclabornia honors Barbara and Alvie Claborn, who discovered and helped prepare the palatoquadrate respectively.[2]
The teeth ofBarbclabornia are similar to those ofBransonella, and as such are believed to be related.[5] They are very small, being between 1–3 mm tall. They are bicuspid, functionallyhomodont, and characterized by cristated, cylindrical, cone-like cusps. In contrast to other xenacanth species, these teeth have no central cusp. The anterior teeth possess triangular bases, while the lateral and posterolateral teeth have quadrangular bases. These bases are thick, amounting to 30% of the tooth height. Monocuspiddenticles, the largest of which being barely over 2 mm tall, are mostly remarkably claw-like in appearance. These denticles are assumed to be from the mucous membrane fold.[2][5][6]
Barbclabornia is also known from a right palatoquadrate, which contains hundreds of these tiny teeth. The palatoquadrate is 37.5 cm (14.7 in) long and incomplete, but is assumed to have a total length of 45 cm (17.7 in).[2][6] The palatoquadrate is thinner than that of other large xenacanthids, likeOrthacanthus, and has a lighter build. Based on other xenacanths, ifBarbclabornia's total length is 10 to 11 times as long as its jaws, it is estimated to have a total length of 4.5 to 5 m (14 to 15 ft) long. This would make it the largest xenacanthid ever found.[6]
Based on the locations where a majority of specimens have been found, being freshwater dominant andtetrapod-bearing,Barbclabornia is most likely a freshwater species, inhabitingcoastal plains of North America.[2] Combinedδ18OP and87Sr/86Sr measurements confirm thatBarbclabornia was a freshwater inhabitant.[7]
The diet ofBarbclabornia can be inferred from its teeth, jaws, and size. Paleontologist Gary D. Johnson initially proposed that the shark could only bite down on its prey and swallow it whole. This would give it a diet of less active prey, primarily smallfish,amphibians, andarthropods.[2] However, Johnson alongsideJiri Zidek, William May, and Alvie Claborn would instead compare the large xenacanth with numerous tiny teeth to beanalogous tomodernfilter feeding sharks, theBasking Shark andWhale Shark. This would indicate thatBarbclabornia was a filter feeder which would primarily consumezooplankton.[5][6]
| ||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||
.jpg)
