Cretalamna catoxodon, Siversson & Lindgren & Newbrey & Cederström & Cook, 2015

Siversson, Mikael, Lindgren, Johan, Newbrey, Michael G., Cederström, Peter & Cook, Todd D., 2015, Cenomanian-Campanian (Late Cretaceous) mid-palaeolatitude sharks of Cretalamna appendiculata type, Acta Palaeontologica Polonica 60 (2), pp. 339-384 : 370-374

publication ID	https://doi.org/ 10.4202/app.2012.0137
persistent identifier	https://treatment.plazi.org/id/B63E4546-433B-FFB5-FCCB-FC7B6B045FD7
treatment provided by	Felipe
scientific name	Cretalamna catoxodon
status	sp. nov.

Treatment

Cretalamna catoxodon sp. nov.

Figs. 19B, 20–22.

1996 Cretolamna appendiculata (Agassiz, 1843) [partim]; Siverson 1996: 826, pl. 3: 5, 6.

1999 Cretalamna appendiculata (Agassiz, 1843) ; Siverson 1999: fig. 6.1A, B.

Etymology: From Greek catoxys, very sharp, and odus, tooth. The name refers to the unusually sharp cutting edges on the cusp in the first and second lower anterior teeth.

Type material: Holotype: first upper right anterior tooth, WAM 09.6.2, “Main Site” (Fig. 20A). Paratypes: WAM 98.11.7 ( Siverson 1999: fig. 6.1), 09.6.1, 4–7, 9, 15–21, 11.12.2–3, “Main Site”; WAM 09.6.8, “New Site”; WAM 09.6.12, “Camp Site” (see Appendix 2 for locality details).

Type horizon: Surface collected from the uppermost 2–3 m of the Gearle Siltstone (middle Cenomanian).

Type locality: “Main Site”, CY Creek, Giralia Anticline, Western Australia (see Appendix 2 for locality details) .

Additional material.—44 teeth, including WAM 09.6.3, 10– 11, 13, 10.9.7–39, “Main Site”; WAM 10.9.1, “New Site”; WAM 09.6.14, 10.9.2–6, “Camp Site”.

Diagnosis.—Anterior teeth equipped with slender cusp; straight, very slightly curved or moderately distally inclined. Outer margin of cusplets more-or-less vertical on upper anterior teeth. Root symmetrical in labial/lingual views on first

Fig. 20. Otodontid shark Cretalamna catoxodon sp. nov., upper and lower anterior teeth, uppermost Gearle Siltstone, middle Cenomanian (Late Cretaceous), → Zone CC10 a; CY Creek, Giralia Range, Western Australia. A. Holotype, WAM 09.6.2, right A1?; lingual (A 1, stereopair), profile (A 2), labial (A 3, stereopair), and basal (A 4) views. B. Paratype, WAM 09.6.1, right A1?; basal (B 1), lingual (B 2), labial (B 3), and profile (B 4) views. C. Paratype, WAM 09.6.6, left a2?; labial (C 1) and lingual (C 2) views. D. Paratype, WAM 09.6.5, left A2?; basal (D 1), lingual (D 2), labial (D 3), and profile (D 4) views. E. Paratype, WAM 09.6.4, left a1?; labial (E 1, stereopair), lingual (E 2), basal (E 3), and profile (E 4) views. F. Paratype, WAM 09.6.8, left a2?; labial (F 1), profile (F 2), and lingual (F 3) views .

upper and lower anterior teeth but asymmetrical in basal view with one lobe more compressed than the other. Lingual protuberance of root poorly demarcated in basal view in upper anterior teeth but highly protruding in profile view, overhanging the neck. Most upper lateroposterior teeth equipped with rounded cusplets, lacking distinct apex.

Description.— First upper anterior tooth file: Four teeth are referred to the first upper anterior file. They are all similar in size and overall morphology and can be characterised by their symmetrical or near-symmetrical root and very slightly distally curved or inclined cusp. One of the teeth is nearly perfectly preserved and designated as holotype for this species (Fig. 20A). It is slightly larger than the other three teeth and, at 24 mm in height, is the largest tooth of this species in our collection. The lobes of the root are more acute in the other three teeth (Fig. 20B 3), but this is probably largely a result of their slightly corroded preservation. The lateral cusplets are small with a rather blunt apex on all four teeth. The root is massive in the well-preserved holotype with a prominent lingual protuberance overhanging the neck (Fig. 20A 2).

Second upper anterior tooth file: A single tooth is assigned to this file (Fig. 20D). The apex is worn down, almost certainly from prey manipulation, and as preserved, the tooth measures 17 mm in height. The cusp is markedly distally bent. As in the teeth assigned to the first upper anterior file, the cusplets are very small. The root is nearly symmetrical in labial/lingual views with a slightly less tightly curved basal edge of the root in labial/lingual views, compared to the teeth referred to the first upper anterior file.

Upper lateroposterior teeth: Teeth, from this part of the jaw, have a slender but labiolingually thick, slightly recurved ( Fig. 21A View Fig 2 View Fig ) to strongly distally curved cusps (more posteriorly situated teeth; Fig. 21G View Fig 3 View Fig ). The lateral cusplets are low with an unusually blunt and poorly defined apex in most teeth (e.g., Fig. 21D View Fig 1 View Fig ). The cutting edges are sigmoidal (most anteriorly situated teeth; Fig. 21A View Fig 3 View Fig ) to straight in profile view Fig. 21E View Fig 2 View Fig ). The median indentation of the basal edge of the root is of C. deschutteri type, forming a wide V with a round- ed apex. In basal view, the lingual protuberance is wide but poorly demarcated from the rest of the root’s lingual edge Fig. 21E View Fig 4 View Fig ).

First lower anterior tooth file: A single, 18 mm high tooth is referred to this file. The tooth has a bleached enameloid and has sustained some corrosion of the root along the lingual root-neck boundary and on the inside of one of the lobes (the latter damage is minor). Apart from these slight imperfections the tooth is well preserved. The cusp is symmetrical and narrow. Its middle third is mesio-distally concave (Fig. 20E 1). There is one pair of small cusplets. The root is massive, nearly perfectly symmetrical and with a large lingual protuberance. The extremities of the lobes are rather acute.

Second lower anterior tooth file: Two teeth are referred to the a2 file. One, 22 mm high, is somewhat corroded (Fig. 20F), whereas the other, larger tooth is severely corroded Fig. 20C). The latter measures nearly 23 mm in height but would have been 24–25 mm high originally. The two teeth differ from the assigned a1 tooth by their asymmetrical root and wide-based cusp.

Lower lateroposterior tooth files: The cusp is relatively upright in lower lateroposterior teeth and the cusplets have typically a well-defined apex. The root is deeper in lower jaw teeth than it is in the corresponding upper jaw teeth ( Figs. 21G View Fig 3 View Fig , 22E View Fig 2 View Fig ) and does not expand laterally beyond the lateral demarcation of the crown to the same extent as it does in upper lateroposterior teeth ( Figs. 21D View Fig 1 View Fig , 22B View Fig 1 View Fig ).

Remarks.— Cretalamna catoxodon sp. nov. cannot readily be placed in any of the three species groups recognised in the Turonian–Campanian of the Northern Hemisphere. Its teeth resemble those of the slender-toothed C. ewelli sp. nov. from the Smoky Hill Chalk in some aspects but differs, e.g., in lacking a typical A3 tooth with a labially curved cusp in profile view and a labiolingually compressed distal lobe of the root. Lateroposterior teeth of C. catoxodon sp. nov., particularly in the upper jaw, differ from those of C. ewelli sp. nov. by having blunt cusplets in a much larger percentage of the teeth. The putative third upper jaw tooth in C. catoxodon sp. nov. has a sigmoidally curved cusp in profile view and possess a distal lobe much thicker than that in C. ewelli sp. nov.

Underwood et al. (2011: fig. 4) illustrated six teeth from the early Cenomanian part of the Karai Formation of the Cauvery Basin, Tamil Nadu, India, as Cretalamna appendiculata . We disagree with the assigned position of at least one of the teeth (Underwood et al. 2011: fig. 4C, D), which they cautiously referred to the third lower anterior file. The shape of the root and the slightly recurved cusp indicates that it is the third upper jaw tooth. Third lower jaw teeth in Cretalamna would typically have a more robust root with a rather tightly curved basal edge in labial/lingual views. One of the teeth referred to the first lower lateral file (Underwood et al. 2011: fig. 4E, F) might be a LP1 or LP2 but the lack of profile and basal images makes it difficult to fully evaluate the positional assignment of the tooth. Teeth of C. catoxodon sp. nov. with a near-identical labial/lingual outline have a profile view typical of upper jaw teeth ( Fig. 21B View Fig 2 View Fig ); although, probable first lower lateroposterior teeth have a similar labial/ lingual outline. The latter differ in profile view from the corresponding upper jaw teeth by their slightly lingually curved cutting edges and more protruding protuberance ( Fig. 22A View Fig ). The median indentation of the basal edge of the root is deeper in probable lp1s than it is in the corresponding upper jaw teeth. The Indian taxon appears to represent an undescribed species of Cretalamna .

Geographic and stratigraphic range.—Middle Cenomanian part of the Gearle Siltstone, Giralia Range and Cenomanian? (source rock uncertain), lower Murchison River area, Western Australia, Australia.