Bottosaurus Agassiz, 1849
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https://doi.org/ 10.4202/app.01117.2023 |
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https://treatment.plazi.org/id/03E18741-130A-EF10-DF1E-FE75FE61FDB1 |
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Felipe |
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Bottosaurus Agassiz, 1849 |
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Genus Bottosaurus Agassiz, 1849
Type species: Crocodilus harlani von Meyer, 1832 , Maastrichtian and Danian, Fieldsboro, New Jersey, USA .
Bottosaurus harlani (von Meyer, 1832) Fig. 4A–C View Fig .
Material.—A relatively large, isolated posterior tooth (RU- EFP-02450), a left juvenile dentary (RU-EFP-03820), and two small partial crowns (RU-EFP-03876, 4169) from the MFL. All from Danian, Edelman Fossil Park, Mantua Township, New Jersey, USA.
Description.—RU-EFP-02450 is large, measuring 56.8 mm in height and 24.0 mm in mesiodistal width. The crown itself is short and blunt, measuring only 12.7 mm in height. The tooth is strongly labiolingually compressed, making the crown subrectangular in cross section. The enamel is strongly folded and exhibits abundant apical striations, giving the crown a wrinkled appearance. A modest, smooth carina is present on the mesial and distal edges of the crown. This keel extends to the base of the crown and would likely have extended over the tip of the tooth, which is worn. Enamel extends slightly further down the root on the lingual side than the labial side.
The left dentary (RU-EFP-03820) is significantly smaller than any previously described specimen of the genus, measuring approximately 58.2 mm ( Fig. 4C View Fig ). Its mandibular symphysis is intact, but its rostral and posterior regions are damaged, making the exact number of alveoli difficult to determine. The specimen possesses either 11 or 12 alveoli with the largest being the most-posteriorly positioned. Based on the morphology of the articulation facet for the splenial, the splenial possessed an anterior tip that passed dorsal to the Meckelian groove, but did not contribute to the mandibular symphysis. The mandibular symphysis extends posteriorly to about the fourth or fifth alveolus, and the tooth row forms a gentle, medially-concave curve between the?fourth and?tenth alveolus.
Two small isolated teeth (RU-EFP-03876, 4169) were also recovered within relatively close proximity (~ 4 m) to the dentary. Each is incomplete, consisting of most of the crown and a small portion of the root (e.g., Fig. 4B View Fig ). They are similar to RU-EFP-02450 in being labiolingually compressed, possessing wrinkled enamel with apicobasallyaligned striations, and development of distinct mesial and distal carinae. Their morphology suggests that they are posterior teeth and are of the appropriate size to have derived from the dentary.
Remarks.—RU-EFP-02450 differs from durophagous mosasaurs in that the base of the crown is not inflated and by its lack of multiple cusps, as seen in the mosasaur Carinodens (e.g., Schulp et al. 2004). Of the five crocodilians known from the Hornerstown Formation, namely Hyposaurus Owen, 1849 , cf. Procaimanoidea Gilmore, 1946 , Bottosaurus , Thoracosaurus Leidy, 1852 , and Borealosuchus Brochu, 1997 ( Gallagher 2003; Brochu et al. 2012), only Bottosaurus possesses similar blunt, crushing-style teeth. In particular, RU-EFP-02450 is assigned to Bottosaurus harlani based on its large size, short and blunt crown, and wrinkled enamel, each of which are characteristic of this taxon ( Cossette and Brochu 2018). This specimen is nearly identical to the paralectotype ( ANSP 9174) and to the teeth described from a new, partially-articulated specimen of Bottosaurus harlani from the MFL in the EFPQ ( Cossette and Brochu 2018).
Although the dentary (RU-EFP-03820) is incomplete, its morphology is inconsistent with that of Borealosuchus because the mandibular symphysis extends posterior to the fourth alveolus and the ninth alveolus is distinctly larger than the eighth. In Borealosuchus , alveoli diameter doesn’t increase until the tenth alveolus. The majority of the complete alveoli in our specimen are slightly labiolingually compressed (~20%), implying that the teeth within them would also have been compressed, consistent with the genus Bottosaurus ( Cossette 2021) .
Bottosaurus harlani is a rare and enigmatic caimanine known only from the Maastrichtian to early Danian of the Atlantic Coastal Plain ( Erickson 1998; Schwimmer et al. 2015; Cossette and Brochu 2018). Bottosaurus harlani has previously been described from the MFL by Gallagher (1993) and Cossette and Brochu (2018), yet the small dentary described here represents the first juvenile remains for this taxon. The morphology of RU-EFP-03820 is strikingly consistent with that of adult specimen NJSM 11265 ( Cossette and Brochu 2018: fig. 5), indicating that this alligatorid acquired its mandibular morphology early in life.
Stratigraphic and geographic range.—Upper Cretaceous (Maastrichtian) to lower Paleocene (Danian) of New Jersey, USA.
Squamata Oppel, 1811
Genus Mosasaurus Coneybeare, 1822
Type species: Mosasaurus hoffmannii Mantell, 1829 , Maastrichtian , Maastricht, Netherlands .
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Academy of Natural Sciences of Philadelphia |
No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.
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