Cretalamna sarcoportheta, 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 : 346-353

publication ID	https://doi.org/ 10.4202/app.2012.0137
persistent identifier	https://treatment.plazi.org/id/B63E4546-4323-FF98-FCCB-F89B6E0C5C6D
treatment provided by	Felipe
scientific name	Cretalamna sarcoportheta
status	sp. nov.

Treatment

Cretalamna sarcoportheta sp. nov.

Figs. 4–8 View Fig View Fig View Fig View Fig View Fig , 19C.

1977 Cretolamna appendiculata var. pachyrhiza [partim]; Herman

1977: 210–216, pl. 9: 3e (non figs. 3a–d [ C. borealis ], 3f, g [undescribed Cretalamna and/or Otodus ex gr. obliquus ]).

1992 Cretolamna appendiculata (Agassiz, 1843) [partim]; Siverson 1992a: 528, pl. 1: 1–4, 9–13, 16–17 (non figs. 5–8, 14, 15 [ Cretalamna borealis ]).

Etymology: From Greek sarkos, flesh, and porthetor, destroyer; destroyer of flesh.

Type material: Holotype: Second upper left anterior tooth, LO 10888T

( Fig. 4D View Fig ). Paratypes: LO 6347t, 6348t, 6351t, 10889t – 10920t ( Figs. View Fig

4A–C, E, F, 5A–H View Fig , 6A–E View Fig , 7A–C View Fig , 8A–J View Fig , 19C: lp7; Siverson 1992a: pl.

1: 1–4, 11).

Type horizon: Unknown horizon within an up to 2 m thick sequence of poorly consolidated calcareous sand of latest early Campanian age

(informal Belemnellocamax mammillatus belemnite zone), Late Cretaceous.

Type locality: Åsen , Kristianstad Basin, southern Sweden .

Additional material.—216 teeth from the informal Belemnellocamax mammillatus zone (latest early Campanian), Åsen locality, Kristianstad Basin, southern Sweden (LO 6352t, 6354t, and 10921t – 11134t).

Diagnosis. —Robust anterior teeth with thick, moderately tall, triangular cusp; either straight, somewhat distally inclined or very slightly curved/recurved. Root asymmetrically subtriangular in basal view in anterior teeth with one lobe considerably broader than other lobe. Cusp very broad and triangular in anteriorly situated lateroposterior teeth with flat labial face of cusp in profile view. Cusp narrower, generally more upright in lateroposterior teeth with slightly lingually curved cusp in profile view. Root markedly asymmetrical in basal view in anteriorly situated upper lateroposterior teeth with distal lobe narrower than mesial lobe in all but one tooth type. Latter, distinct tooth type with apically curved cusp and sub-rectangular root in basal view, with root-lobe on same side of vertical mid-line of tooth as apex of cusp more compressed than other lobe.

Description.— Parasymphyseal teeth: There are no complete parasymphyseal teeth from the Åsen and Ignaberga localities as the root is corroded to a variable degree in all specimens. The cusp is thick, triangular and set at an angle ( Siverson 1992a: pl. 1: 16). Some teeth have at least one small, triangular cusplet ( Siverson 1992a: pl. 1: 13; Fig. 19C). The root is asymmetrical in basal view with one side being thinner than the other. The thinner root-lobe is on the same vertical side of the tooth in lingual/labial views as the apex of the inclined cusp ( Siverson 1992a: fig. 12).

First upper anterior tooth file: Three complete teeth are referred to this tooth file (additional to several incomplete specimens). They measure 17.5, 18.5 and 19 mm in height. The cusp is labiolingually very thick, even more so than in the first lower anterior tooth. The cusp is straight ( Fig. 4B View Fig 1 View Fig ) to moderately distally curved ( Fig. 4A View Fig 1 View Fig ). The cusplets are

LO 10898t, right LP3 ?; basal (E 1), lingual (E 2), profile (E 3), and labial (E 4) views. F. Paratype, LO 10899t, left LP3 ?; basal (F 1), labial (F 2), profile (F 3), and lingual (F 4) views. G. Paratype, LO 10900t, right LP4 ?; labial (G 1), profile (G 2), and lingual (G 3) views. H. Paratype, LO 10901t, right LP4 ?; lingual (H

), profile (H

), and labial (H

) views.

small on all first upper anterior teeth and divergent to sub-parallel to the vertical axis of the cusp. The neck is rather narrow and of even apico-basal width along the entire root-crown boundary. The root is symmetrical in labial/lingual views but variable in both total width and the width of the lobes. The distal lobe of the root is labiolingually compressed relative to the inferred mesial lobe ( Fig. 4A View Fig 3 View Fig , B 2 View Fig , C 1 View Fig ).

Second upper anterior tooth file: Three complete teeth are referred to this tooth file (additional to several incomplete specimens), measuring 16.5–17 mm in height. The

cusp is triangular, labiolingually moderately compressed and straight ( Fig. 4D View Fig 3 View Fig ) to somewhat distally inclined ( Fig. 4F View Fig 2 View Fig ) with a very slightly recurved apex. The cusplets are small and more-or-less divergent. The root is markedly asymmetrical with a broad mesial lobe and narrower, shorter and less divergent distal lobe. In labial and lingual views, the basal edge of the mesial lobe is straight to slightly convex whereas the basal edge of the distal lobe is straight to slightly concave. The “maximum root width/tooth height ratio” is larger in the second upper anterior teeth than it is in the first upper anterior teeth, as the former are slightly shorter on average but at the same time somewhat wider.

Upper lateroposterior tooth files: The first upper lateroposterior tooth has a distinctive morphology in this species. The cusp is vertical in its basal half but has a slightly to moderately distally curved apex ( Fig. 5A View Fig 1 View Fig ). The root is asymmetrical, displaying a sub-vertical, rounded mesial lobe and a broader, more angular distal lobe. The mesial lobe is markedly compressed labiolingually ( Fig. 5A View Fig 2 View Fig ), presumably a result of a position adjacent to an intermediate bar. The root is likewise asymmetrical in the second upper lateroposterior tooth, featuring a sub-quadrangular distal lobe and a more acute mesial lobe. Putative second upper lateroposterior teeth have a straight to slightly concave profile view ( Fig. 5B View Fig 4 View Fig , C 2 View Fig ). As reconstructed ( Fig. 19C), the root becomes increasingly more symmetrical moving posteriorly through the upper jaw files and reaches near-perfect symmetry in the middle part of the lateroposterior row ( Fig. 5G View Fig 3 View Fig ). Posteriorly, beyond this point, the root becomes increasingly more asymmetrical again exhibiting an enlarged mesial lobe ( Fig. 6D View Fig 1 View Fig ). The cusp is slightly distally inclined in the mesial half of the files and distally curved rather than inclined in most teeth in the posterior half of the lateroposterior files. In basal view, the distal lobe of the root is typically compressed, relative to the mesial lobe, in anteriorly situated upper lateroposterior teeth ( Fig. 5B View Fig 2 View Fig , E 1, F 1 View Fig ).

First lower anterior tooth file: A near perfectly preserved tooth along with an incomplete specimen, in addition to several less well preserved teeth, are referred to the first lower anterior tooth file ( Fig. 7A, B View Fig ). The well preserved tooth is a nearly 19 mm high, symmetrical tooth. The tightly curved basal edge of the root and the symmetry of the specimen indicate that it originates from the first anterior file. One of its lateral cusplets is rudimentary whereas the other one is small but well formed. The tooth is assigned to the first lower rather than the first upper anterior file on the basis of its massive root with a large lingual protuberance and a somewhat lingually curved cusp, although the difference in curvature of the cusp in profile view between inferred upper and lower anterior teeth is relatively minor in this species. As far as can be determined from its incomplete preservation, the other tooth referred to this position is very similar to the complete tooth.

Second lower anterior tooth file: A large, incomplete tooth (additional to several other, even more incomplete teeth) is referred to this file ( Fig. 7C View Fig ). As preserved, the tooth measures just over 21 mm in height and would have been about 22 mm high originally. The distal portion of the mesial lobe of the root is incomplete but the tooth is otherwise well preserved. The cusplets are divergent and larger than those of the other anterior teeth. The massive cusp is distally bent and the preserved distal lobe of the root is rectangular. The neck is relatively narrow as in other anterior teeth of this species. The basal edge of the root is V-shaped. The lingual protuberance of the root is prominent.

Lower lateroposterior tooth files: The most mesially locat- ed lower lateroposterior teeth feature a distally directed cusp e.g., Fig. 8C View Fig 1 View Fig ). Moving posteriorly through the lower jaw teeth the cusp becomes progressively lower and more symmetrical. The root is markedly asymmetrical in the first two or three lateroposterior files, with a short, rounded to quadrangular distal lobe and an elongated tapering mesial lobe, but becomes increasingly more symmetrical in more posteriorly situated teeth. The lower lateroposterior teeth differ from upper lateroposterior teeth by their straight to lingually curved labial face of the cusp in profile view (as opposed to a straight to labially curved labial face) and generally more upright cusp.

Remarks.—See the description of C. appendiculata above for a comparison with the closely related C. sarcoportheta sp. nov.

The teeth of C. sarcoportheta sp. nov. differ in several aspects from those of the coexisting C. borealis . The teeth of the latter species reach a much larger size, with anterior teeth measuring up to an estimated 38–40 mm in height in the Kristianstad Basin population ( Fig. 9A View Fig ) compared to about 23 mm (first upper anterior tooth) for a much larger sample of C. sarcoportheta sp. nov. teeth. The anterior teeth of C. sarcoportheta sp. nov. have a comparatively short, robust cusp ( Fig. 19C) and a massive root (e.g., Fig. 7A View Fig 3 View Fig ), whereas the cusp is very tall and relatively slender in small to medium-sized (relatively speaking) anterior teeth of C. borealis Fig. 9B, C View Fig ). Scaled down in size to the same height as the anterior teeth of C. sarcoportheta sp. nov., anterior teeth of C. borealis up to about 32–33 mm in height are gracile by comparison. Above that size the cusp becomes broader in C. borealis and the root increases exponentially in thickness approaching maximum tooth height/width in both anterior and lateroposterior teeth. The cusp on teeth of C. borealis has typically a more convex labial face than in teeth of C. sarcoportheta sp. nov. This is taken to the extreme in earliest early Campanian C. borealis ( Gonioteuthis granulataquadrata Zone , conglomerate C, Ullstorp 1 quarry; see Lindgren et al. 2007: 930) in which the labial face is occasionally more convex than the lingual face in some of the lager lateroposterior teeth. The lateral cusplets are often more divergent in C. borealis and the inner edge is commonly strongly convex Fig. 9D View Fig 4 View Fig , E 3 View Fig ). In basal view the root is rectangular in upper lateroposterior teeth of C. borealis ( Fig. 9E View Fig 4 View Fig ) but asymmetrical with a compressed distal lobe (compressed mesial lobe in inferred LP1) in the majority of anteriorly situated upper lateroposterior teeth of C. sarcoportheta ( Fig. 5B View Fig 2 View Fig , E 1, F 1 View Fig ).

Agassiz’s (1843) “ Otodus ” latus (sensu Herman 1977) is clearly a distinct, Maastrichtian species. However, it needs to be defined on the basis of homogeneous material, collect- ed from a narrow stratigraphical interval, from northwest Europe. Its teeth are larger in absolute terms and wider in relative terms than are those of latest early Campanian C. sarcoportheta sp. nov. The cusplets are lower and, on average, smaller in the Maastrichtian species and they may lack a well-defined apex ( Herman 1977: pl. 9: 4c). The mesial and distal lobes of the root in lateroposterior teeth are separated by a rather conspicuous median indentation in C. sarcoportheta sp. nov., whereas the median indentation is rather shallow in C. lata . Although it is probable that C. lata belongs to the C. appendiculata group it is in need of revision.

Cretalamna sarcoportheta sp. nov. differs from C. arambourgi Cappetta and Case (1975) from the Danian? of Youssoufia, Morocco, by having upper anterior teeth with a broader cusp relative to the width of the root and a more protruding lingual protuberance in profile view (compare Fig. 4 View Fig and Arambourg 1952: pl. 14: 1, 14), lower anterior teeth with a wider cusp and more robust root (compare Fig. 7 View Fig and Arambourg 1952: pl. 14: 12, 13), and a shallower median indentation of the basal edge of the root in both anterior and lateroposterior teeth. Several of the lateroposterior teeth illustrated by Arambourg (1952) have a second, minute pair of lateral cusplets whereas almost all lateroposterior teeth of C. sarcoportheta sp. nov. have only a single pair of cusplets.

The reconstruction of the lateroposterior part of the dentition in C. sarcoportheta sp. nov. with ten upper jaw tooth files (LP10 not shown in Fig. 19C as all presumed LP10s available to us are poorly preserved) is based on anterior/ lateroposterior tooth ratios for the collected material from the Åsen locality and should be regarded as nothing more than a rough approximation.

The synonymy list is restricted to records near the early/ late Campanian boundary of northwest Europe. All previous reports of isolated teeth of C. appendiculata type need re-evaluation. Siverson (1992a) noted the presence of lowcusped, small Cretalamna teeth (i.e., C. sarcoportheta sp. nov.) co-occurring with large, tall-cusped Cretalamna teeth (i.e., C. borealis ) in the informal Belemnellocamax mammillatus zone of the Kristianstad Basin. In order to accommodate both morphologies within the accepted species concept of C. appendiculata of that time, Siverson (1992a) envisioned a somewhat unlikely ontogenetic development whereby the cusp grew relatively slimmer with increasing age of the shark.

The late Campanian/early Maastrichtian teeth from New Jersey, USA, illustrated as C. appendiculata lata by Cappetta and Case (1975: pl. 3: 10–27) are close in morphology and tooth-type range to C. sarcoportheta sp. nov. In the absence of a thorough revision of the dentally similar C. lata and precise stratigraphical data for the New Jersey material, it is probably unproductive to elaborate any further on the identification. The same applies to the vast majority of previous records of Cretalamna of C. appendiculata type, as these accounts invariably lack teeth with pristine root preservation illustrated in basal and profile views (the most diagnostic views in this group of sharks as long as the root is perfectly preserved).

Geographic and stratigraphic range.—Campanian of Sweden (Scania Province), Belgium (Hainaut Province) and France (Beauval quarry, Picardie Province; Pieter De Schutter collection).