Globidens
| Globidens | |
|---|---|
| |
| Skull of G. dakotensis (bottom view) in the Field Museum of Natural History, Chicago. | |
Scientific classification 
| |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Clade: | †Mosasauria |
| Superfamily: | †Mosasauroidea |
| Family: | †Mosasauridae |
| Tribe: | †Globidensini |
| Genus: | †Globidens Gilmore, 1912 |
| Species | |
| |
Globidens ("Globe teeth") is an
Globidens alabamaensis was the first species of Globidens described, in a publication by Charles W. Gilmore (1912). It is used as the type specimen for Globidens.
Globidens belongs to the family
Description
Globidens was a relatively medium-sized mosasaur, measuring about 5–6 metres (16–20 ft) long.
Gilmore's initial assessment of Globidens, based on an incomplete specimen of G. alabamaensis, made note of characteristics observable in parts of the skull, the teeth, and one of the cervical vertebrae. He made note of a long snout with a large maxilla, a large, sturdy frontal bone, and the characteristic globular teeth with finely wrinkled enamel. Gilmore concluded that the skull characters were similar to Platecarpus or, more closely, to Brachysaurus (which is currently Prognathodon).
Studies since Gilmore's assessment establish more specific and more complete lists of diagnostic features. Gilmore correctly inferred that Globidens had a stout, powerfully built skull. In addition, a few of its notable skull characteristics include a small parietal foramen located entirely within the parietal, tuberosities present on the
History of discovery
Globidens was first described in 1912 by Charles W. Gilmore. Using an incomplete specimen made of only of a partial skull with several teeth, a single cervical vertebra, and numerous fragments, Gilmore identified Globidens as a new genus and named his type specimen Globidens alabamaensis. The genus name was based on the globular structure of the specimen's teeth and the species name on the location in which it was discovered: Alabama. However, it may be noted that the original location from which the specimen was taken is not precisely known, as Gilmore was examining a specimen that had been collected earlier.[4]
Since Gilmore's identification of Globidens, several other species have been identified, including G. dakotensis (Russel 1975), which is sometimes used as a secondary type specimen alongside G. alabamaensis. Some specimens previously thought to be new species of Globidens have since been reassigned to other taxa, such as Prognathodon, or placed in a new taxa, such as G. aegypticus, which is now a type specimen for Igdamanosaurus.[5]
Species
- Globidens alabamaensis Gilmore, 1912 - (Generic type) The height of the tooth crown is less than the greatest tooth crown diameter behind the seventh maxillary tooth. The crown length is greater than the crown width in front of the tenth maxillary tooth. The maxilla is long and the frontal is narrow. The frontal bone slightly enters the orbits dorsally.[3]
- G. dakotaensis Russell, 1975 - The height of the tooth crown is less than the greatest tooth crown diameter behind the fourth maxillary tooth. The crown length is greater than the crown width in front of the tenth maxillary tooth. The maxilla is long and the frontal is broad. The frontal bone does not enter the orbits dorsally.[3]
- G. phosphaticus Bardet et al. 2005[6] from Morocco and Angola.[1]
- G. schurmanni Martin, 2007.
- G. hisaensis Kaddumi, 2009 from central Jordan.[7]
- G. simplex LeBlanc et al. 2019 from Morocco. A complete mandible and partial skull was recovered, showing large jaw adductor musculature attachment points indicative of hard shelled prey. A shortened dentary with respect to the Posterior Mandibular Unit relative to other globidensine mosasaurs supports this as well. Postcranial remains were also recovered and histological analysis of one rib showed increased bone compactness reminiscent of conditions seen in early stages of marine tetrapod evolution, suggesting increased ability to stay submerged for long periods along the sea floor.[8]
Reassigned species
- Globidens aegyptiacus Zdansky, 1935;[9] now type species of Igdamanosaurus.[5]
- Globidens fraasi Dollo 1913; now type species of Carinodens.[10]
- Globidens timorensis Huene, 1935; reinterpreted as a ichthyosaur[11]
Classification
Globidens resides within the subfamily Mosasaurinae, which includes several mosasaur lineages, and within that, the Tribe Globidensini, which also includes the genus Carinodens.[3] Carinodens is thus regarded as a sister taxon of Globidens.
Placement of Globidens and, to an extent, Mosasauridae in a phylogenetic tree is somewhat unclear and specific placement of genera varies between many morphological and molecular tests. It is generally agreed that Mosasauridae is a sister group to Pythonomorpha, which includes all snakes.[12] Within Mosasauridae, Globidens is generally placed near Prognathodon, although some placements of Prognathodon specimens are questionable.[13]
Below is a cladogram of mosasaurs and related taxa modified from Aaron R. H. Leblanc, Michael W. Caldwell and Nathalie Bardet, 2012:[13]
| Mosasaurinae |
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Paleobiology
Globidens was uniquely adapted to take advantage of hard-shelled prey in comparison to other mosasaurs. In addition to a generally robust skull,
Paleoecology
Globidens, like other mosasaurs, lived in the warm, shallow seas of the Late Cretaceous, such as the Western Interior Seaway of North America. So far, Globidens has been discovered primarily in North America and in parts of northern and western Africa, such as Morocco and Angola, although specimens from the Middle East and eastern South America have been found as well.[6][16]
See also
References
- ^ .
- .
- ^ a b c d e f Russel, Dale (1975). "A new species of Globidens from South Dakota, and a review of globidentine mosasaurs". Fieldiana Geology. 33 (13): 235–256.
- ^ Gilmore, Charles W. (1912). "A new mosasauroid reptile from the Cretaceous of Alabama" (PDF). Proceedings of the United States National Museum. 41 (1870): 479–484.
- ^ a b Lingham-Soliar, T. (1991). "Mosasaurs from the Upper Cretaceous of Niger". Palaeontology. 34 (3): 653–670.
- ^ .
- OCLC 709582892.
- .
- ^ Zdansky, O. 1935. The occurrence of mosasaurs in Egypt and in Africa in general. Bulletin de l’Institut d’Egypte 17: 83-94.
- ISSN 0272-4634.
- .
- ^ Caldwell, M. W. 1999. Squamate phylogeny and the relationships of snakes and mosasauroids. Zoological Journal of the Linnean Society, 125(1):115-147
- ^ .
- ^ Massare, J. A. 1987. Tooth Morphology and Prey Preference of Mesozoic Marine Reptiles. Journal of Vertebrate Paleontology, 7(2):121-137.
- ^ Polcyn, M. J., Jacobs, L. L., Schulp, A. S., and Mateus, O. 2010. The North African Mosasaur Globidens phosphaticus from the Maastrichtian of Angola. Historical Biology, 22(3):175-185.
- Everhart, M.J. 2008. Rare occurrence of a Globidens sp. (Reptilia; Mosasauridae) dentary in the Sharon Springs Member of the Pierre Shale (Middle Campanian) of Western Kansas. p. 23-29 in Farley G. H. and Choate, J.R. (eds.), Unlocking the Unknown; Papers Honoring Dr. Richard Zakrzewski, Fort Hays Studies, Special Issue No. 2, 153 p., Fort Hays State University, Hays, KS.[page needed]
- Huene, E. von. 1935. Mosasaurier-Zähne von Timor. Centralblatt fur Mineralogie. Geologic und Palaeontologie; in Verbindung mit dens Neuen Jahrbuch fur Mineralogie, Geologie und Palaeontologie. Stuttgart. Abt. B 10 412-416, 3 figs. (in German)
- Martin, J. E. 2007. A new species of the durophagous mosasaur, Globidens (Squamata: Mosasauridae) from the Late Cretaceous Pierre Shale Group of central South Dakota, USA. Pages 167-176 in Martin, J. E. and Parris D. C. (eds.), The Geology and Paleontology of the Late Cretaceous Marine Deposits of the Dakotas. Geological Society of America, Special Paper 427. (Globidens schurmanni)
- Russell, Dale A. 1975. A new species of Globidens from South Dakota. Fieldiana Geology, 33(13): 235-256. (Field Museum of Natural History)