Heslerodus divergens ( Trautschold, 1879 )

Ginter, Michał, 2002, Taxonomic notes on “ Phoebodus heslerorum ” and Symmorium reniforme (Chondrichthyes, Elasmobranchii)., Acta Palaeontologica Polonica 47 (3), pp. 547-555 : 548-551

Heslerodus divergens ( Trautschold, 1879)

Figs. 1A–C , 2A–G .

Cladodus divergens Trautschold ; Trautschold 1879: 51, pl. 6: 11.

Phoebodus sp. ; Case 1973: fig. 47.

Phoebodus n. sp.; Zangerl 1981: figs. 56–58.

“ Cladodus ” sp.; Schultze 1985: fig. 3.5.

Phoebodus heslerorum sp. n.; Williams 1985: 124–131, figs. 22–23, pls. 16, 17.

“ Cladodus ” divergens Trautschold ; Ivanov1999:276–277,fig.3,pl.7:1.

Holotype: The largest and most complete of three specimens (herein designated as a, b, c) catalogued under the same museum number PCh/617 at the Institute of Zoology , Wrocław University , Wrocław, Poland ( Fig. 1A ). The specimen was described and figured by Trautschold (1879: 51, pl. 6: 11).

Type locality and horizon: Moscow Region, Myachkovo, Upper Carboniferous, Upper Moscovian , Myachkovian Regional Stage .

Original diagnosis (translated from Trautschold 1879).—In the limestone from Mjatschkowo there occur small teeth of Cladodus which totally differ from the others; the median cusp is not as large as in usually found Cladodus teeth and the lateral cusps are curved sidewards. The figured specimen is a typical representative of this species. Both lateral cusps are almost as high as the median cusp and strongly diverge sidewards; the smaller intermediate cusplets are also divergent, but less than the lateral cusps, and the main median cusp runs straight upwards with a slight lingual bend.

Emended diagnosis.—Sharks bearing teeth whose crown is composed of three long, recurved main cusps, and usually two intermediate, smaller cusplets. The median cusp is slightly larger than the lateral main cusps or equal to them in size. The lateral cusps are sigmoidal and strongly divergent mesio−distally, at about 80–90 degrees between each other. The base is rounded, with a distinct labial concavity and usually two buttons on the apical side of the lingual torus.

Description.—Thus far Heslerodus divergens was found from seven regions in the world and these records will be mentioned here in a following order: the type material from Myachkovo, Moscow Region ( Trautschold 1879); the type material of “ Phoebodusheslerorum ” from Indiana ( Williams 1985); teeth from Peru, Nebraska ( Case 1973; Ossian 1974); from Ohio and Pennsylvania ( Hansen 1986); from Kansas ( Schultze 1985) and from boreholes in Moscow Region and Pechora Sea ( Ivanov 1999). Anew specimen from Haystack Range in Wyoming (C. Sandberg’s coll.) will also be described.

The type material of H. divergens from Myachkovo consists of three black, five−cusped teeth, embedded in small pieces of white limestone. Only labial views of the teeth are visible. The largest tooth ( Fig. 1A ; the holotype, illustrated and described by Trautschold 1879) has all five cusps preserved almost to the tips and covered with shiny enameloid. The lateral main cusps reach about 3/4 of the length of the median cusp which is also a little thicker. The lateral cusps curve mesio−distally: the angle between their proximal parts is about 80 degrees, but closer to the tips it almost reaches 90 degrees.Themaincuspsseemtohaveprimaryandsecondary ornamentation. On each cusp there are two strong cristae joiningdistally,beforereachingthetips,andafew(2–4)gentle, subparallel striae. The striae, however, can be only cracks on the enameloid. The intermediate cusplets are very thin and almost smooth. They reach about 2/3 of the length of the lateral cusps. There is a distinct depression in the labial side of the base, below the median cusp. The wavy outline of the base on each side of the depression suggests the presence of two symmetrically placed labio−basal projections. The width of the base is about 3.5 mm.

The second tooth ( Fig. 1B ) is slightly smaller, it lacks the intermediate cusplet on the left side and the tip of the median cuspisabradedstrongerthanintheholotype.Remainsoftwo cristae are visible on the right intermediate cusplet. The angle between the lateral cusps is unusually small compared to the holotype (about45–50degrees).Themediancuspofthethird tooth ( Fig. 1C ) is also worn, so it looks as if it was of equal length to the lateral cusps. However, it is evidently thicker which suggests that it must have been longer as well. Both intermediate cusplets are partially preserved and the angle betweenthemainlateralcuspsisabout60degrees.Theprimary cristation and the labio−basal depression are visible in both the second and the third tooth.

Locality and stratigraphic position: Myachkovo, Moscow Region; Upper Carboniferous, Upper Moscovian , Myachkovian Regional Stage .

The type material of “ Ph. heslerorum ” from Indiana consists of teeth, fin spines, scales, and partially articulated endoskeletons, including braincases and jaws. It was described in detail by Williams (1985), so only the teeth will be reviewed here. Four well prepared teeth were illustrated ( PF 8180, 8322, 2440, 8242; Williams 1985: pl. 16: 1–4, 7, 8), in addition to several scattered around the palatoquadrate, hidden in the black shale and visible only on an X−ray photograph ( PF 8212; Williams 1985: pl. 16: 10). Three teeth ( PF 8180, 8322, 8242) are displayed in labial and/or basal views. All of them possess a distinct labio−basal depression, framed by two rounded projections of moderate size. The median cusp is slightly larger than the main lateral cusps, which form an angle of about 80 degrees between each other. The intermediate cusplets are relatively as long as in the holotype of H. divergens , and in PF 8242 they seem to be even longer. The ornamentation of the labial face of the main cusps consists of subparallel cristae (from 4 in PF 8242 up to 8 in PF 8322) and some of them apparently reach the tips. PF 2440 is figured in lingual view, and two lateral cusps and the occlusal side of the base are visible. The cusps are evidently sigmoidal, their lingual faces seem to be almost smooth, and two separate buttons occur on the lingual torus, rather close to the lingual rim. Currently, after further preparation, it appeared that PF 2440 belongs to a tooth−file with two more teeth lying behind (M.G. personal observation 1997).

The X−rayed teeth ( PF 8212) are characterised by approximately the same size ratio between the cusps as the above described specimens and by strongly divergent lateral cusps. It is possible that two symmetrically placed white spots in the basal area ( Williams 1985: pl. 16: 10, central left) represent labio−basal projections.

There are also a few teeth of H.divergens on a slab with a spine ( PF 8183). They stick out from the rock at different extent. The best visible tooth ( Williams 1985: pl. 17: 2, upper left) probably shows its lingual side, but the lingual torus of thebaseismissing.Thepositionandrelativesizeofthecusps is typical of this species.

Locality and stratigraphic position of illustrated teeth: Hesler, Mecca, and Logan Quarries, Parke County, Indiana; UpperCarboniferous, Desmoinesian (Moscovian),Lintonand Staunton Formations. For other details see Williams (1985) .

Teeth from Peru, Nebraska, were illustrated by Case (1973: fig. 47, as Phoebodus sp. ) and Ossian (1974: pl. 3: 4–6, a tooth from a collection of 476 specimens, as Cladodus occidentalis ). The teeth are almost identical, fairly well preserved, only the tips of the main cusps and distal halves of intermediate cusplets are missing. The angle between the lateral cusps, which are slightly sigmoidal, exceeds 80 degrees, typical of the species. The median cusp is slightly thicker and probably was slightly higher than the lateral cusps before having lost the tip. Since only photocopies of photographs of these teeth are at my disposition, I cannot say much about the ornamentation of the cusps. However, on the labial face of the median cusp two strong cristae are visible, probably joining before the tip ( Case 1973: fig. 47, labial view).

The base is semicircular to slightly triangular, the labio−basal depression and two rounded labio−basal projections are well developed. The buttons on the occlusal side are closely spaced.

Locality and stratigraphic position: Peru, Nebraska; Upper Carboniferous, Onaga Formation, Indian Cave Sandstone.

Teeth from Ohio and Pennsylvania (two five−cusped specimens, OSU 35438–35439) were recorded by Hansen (1986, as Ph. heslerorum ). The teeth are strongly abraded and only basal parts of the cusps are preserved. However, two lingually placed buttons on a semicircular to triangular lingual torus, corresponding to them two rounded labio−basal projections, and a labio−basal depression (“median sulcus” sensu Hansen 1986) are clearly visible. The diameter of the subcircular proximal part of the median cusp is only slightly larger than those of the lateral main cusps. During my visit to Columbus, Ohio, in 1997, I managed to find two more, similar teeth in the unnumbered part of Hansen’s collection ( Fig. 2F, G , new numbers: OSU 50490 and 50491). Their overall appearance and state of preservation resemble those of the other H. divergens teeth from Ohio. It can be added to the characteristics given above that the ornamentation of the labial face of the cusps consists of only a few (3–4) strong cristae, whereas the lingual face is covered by numerous (up to 20? on the median cusp), very gentle cristae.

Localities and stratigraphic position: PA−1, rip−rap blocks (now removed) on east side of Pennsylvania Rte. 286, Allegheny County, Pennsylvania; Gwi−3, exposure on north side of Interstate 70, Guernsey County, Wills Township, Ohio; At−64, exposure along Trimble Township Road 345 to hill top at Athens−Morgan County line, Ohio; Ld−1, quarries of Marquette Cement Company, Lawrence County, Decatur Township, Ohio. Upper Carboniferous; PA−1, Gwi−3, and At−64, Conemaugh Group, Ames limestone; Ld−1, Allegheny Group, Vanport limestone. Hansen (1986) also notes onetoothofthistype( OSU 35440)fromtheWewokaFormation, Oklahoma. For details see Hansen (1986).

A tooth from the Permian of Kansas ( KUVP 82667 ; Schultze 1985: fig. 3.5, “ Cladodus ” sp.) has the lingual part of the base damaged, but the two distinct, rounded, widely separated buttons are preserved. The crown is fairly complete. It consists of three large main cusps, almost equal in size, and two much thinner intermediate cusplets. All the cusps lack their tips. The lateral main cusps are strongly divergent. The ornamentation of the cusps is well preserved, it is composed (as in the case of the specimens from Ohio) of few strong cristae on the labial and numerous delicate cristae on the lingual face. One stronger crista runs along the lateral edges of each cusp. The cristae on the lingual face of the median cusp form a peculiar pattern. They start close to the midline and run laterally, leaving the middle part of the cusp unornamented.

Locality and stratigraphic position: KS Highway 13 roadcut, Pottawatomie County, Kansas; Lower Permian , uppermost Threemile Limestone. For details see Schultze (1985) .

Teeth from boreholes in Moscow Region ( Ivanov 1999: fig. 3D, E,“ Cladodus ” divergens )are largely damaged. Their state of preservation resembles that of the specimens from Ohio. Drawings of only two of five teeth are available. The presence of two buttons and labio−basal projections is evident, but the labio−basal depression is only slightly marked. One of the specimens ( Ivanov 1999: fig. 3D) has the buttons, as well as the labio basal projections, widely separated, in the other ( Ivanov 1999: fig. 3E) the buttons apparently touch each other and the labial projections are closely spaced.

Locality and stratigraphic position: Mytischi 15 and 17, Afonas’evo 9, and Vodniki V 2/3 boreholes, Moscow Region; Upper Carboniferous, Kasimovian.

Atooth from Pechora Sea, figured by Ivanov (1999: fig. 3A, pl. 7: 1; LP 6−61, “ Cladodus ” divergens ), differs from all the above mentioned teeth by the lack of intermediate cusplets in the crown, rounded labio−basal projections, and two separate buttons on the lingual torus. There is only one, ratherflatbutton,surroundedbyaboutsevenforamina.However, the labio−basal depression is present, the cusps are almost equal to each other and the main lateral cusps diverge sidewards at about 40 degrees towards the median cusp. These characters show that the specific identification made by Ivanov (1999) was apparently correct.

Locality and stratigraphic position: borehole Gulyayevskaya, Pechora Sea (Russian Arctic); Upper Carboniferous, Gzhelian or Lower Permian, Lower Asselian.

A tooth from Wyoming, IGPUW /Ps/6/1, collected by C.A. Sandberg ( US Geological Survey, Denver) is a typical representative of the species ( Fig. 2A–E ). The base seems to be almost complete, perhaps only slightly lingually abraded. One of the lateral main cusps is preserved from the base to the tip, the distal half of the other and about 1/3 of the median cusp is broken. The intermediate cusplets lack their tips. The angle between the proximal parts of the lateral cusps is about 80 degrees; the angle between the distal parts probably could reach 90 degrees. The median cusp is thicker, and probably originally it was longer than the lateral cusps. The completely preserved lateral main cusp is sigmoidal. All the cusps bear two strong cristae on their labial faces. The cristae apparently anastomose far below the tip of the median cusp, but on the lateral cusps they run separately almost to the tip. The lingual face of the crown is covered by numerous gentle cristae. In the proximal part of the cusps short intercalating cristae occur. As in the specimen from Kansas a smooth, unornamented area is left in the middle of the lingual face of the median cusp. A blade−like crista runs along the lateral edges of all the cusps. The labio−basal depression and two rounded projections are present. The buttons on the occlusal side of the lingual torus are separate, but rather close to each other. Two major lingual nutritive foramina open below each button. This feature was also noted from the Oklahoma specimen by Hansen (1986). Another, also lingually facing opening of moderate size is placed between the buttons.

Locality and stratigraphic position: sample BAH−4, Steeple Pasture, Haystack Range, Wyoming; Upper Carboniferous , Morrowan (Bashkirian), Idiognathodus sinuosis conodont Zone.

The above presented review shows that the morphology of hitherto found teeth of Heslerodusdivergens is rather uniform, with only a few exceptions, and that they are characterised by the following features:

– the base outline is semicircular to triangular with rounded angles;

– a labio−basal depression (“median sulcus”), with a rounded labio−basal projection on each side, occurs below the median cusp;

– in most cases two distinct, rounded buttons (articular bosses), corresponding to the labio−basal projections, are present on the occlusal (“upper”) side of the lingual torus; the buttons can be widely separated to closely spaced, very rarely they can be fused, forming a single boss;

– the main upper nutritive foramina can perforate the lingual side of the buttons and/or a single, medially placed lingual foramen can occur;

– the crown consists of three recurved main cusps and two intermediate cusplets; very rarely the intermediate cusplets can be absent;

– the median cusp is usually slightly larger than the main lateral cusps;

– the lateral main cusps are sigmoidal; the angle between their proximal (basal) parts is about 80 degrees, but the angle between their distal parts can reach 90 degrees;

– the cusps are rounded proximally and slightly labiolingually compressed distally;

– the ornamentation of the labial side of the cusps is usually composed of only two strong cristae which, on the median cusp, join before reaching the tip; however, several secondary, less distinct cristae can also occur;

– thelingualfaceofthecuspsiscoveredwithnumerousvery gentle cristae; at the basal part additional, short, intercalating cristae can occur; the middle part of the median cusp is smooth;

– a low, blade−like crista, runs along the lateral edges of all the cusps.

Remarks.—The overall appearance of H.divergens , and especially the crown, is similar to that of Famennian phoebodonts, such as Phoebodus politus Newberry, 1899 or Ph. turnerae Ginter and Ivanov, 1992 . That was the reason why Williams (1985) referred to his specimens from Indiana as Phoebodus heslerorum . However, all the species of Phoebodus , including the type species Ph. sophiae St. John and Worthen, 1875 , are characterised by a single, arcuate labio−basal projection and a single button on the upper side of the lingual torus. No trace of a labio−basal depression has been recorded. Moreover, the median cusp in the phoebodonts is always equal to or lower than the lateral cusps, whereas in almost all known specimens of H. divergens the median cusp is slightly larger. The latter feature was pointed out independently by Trautschold (1879) and by Williams (1985: 127).

The presence of two buttons, two labio−basal projections andthe“mediansulcus”suggeststherelationshipbetween H. divergens and “ Cladodus ” occidentalis Leidy, 1859 . Ossian (1974) proposed that these two tooth forms can occur in one individual as lower and upper jaw teeth, respectively. The discovery of partially articulated specimens of H. divergens in Pennsylvanian black shales ( Williams 1985), with only Heslerodus −like teeth dispersed around the jaw cartilages, proved Ossian’s idea improbable. Teeth of several other Late Devonian through Early Permian sharks, probably representing different groups, display similar features, particularly the occurrence of a labio−basal depression. Such teeth will be considered below, in the section dedicated to Symmorium reniforme .

Stratigraphic range.—Late Carboniferous (Bashkirian– Gzhelian),probablythroughtheLowerPermian(Asselian).

Figures

Fig. 1. Shark teeth from Myachkovo, Moscow Region, Russia, Upper Carboniferous, Upper Moscovian. A–C. Heslerodusdivergens (Trautschold, 1879). A. Holotype PCh/617a. B, C. Associated specimens PCh/617b, c (respectively), all in labial views. Scale bar 1 mm. D–F. “Cladodus” occidentalis Leidy, 1859 (= “C.” lamnoides sensu Trautschold 1874). D, E. PCh/425a, occlusal and basal views. F. PCh/425b, labial view. Scale bar 5 mm.

Fig.2. Heslerodusdivergens (Trautschold,1879). A–E.SpecimenIGPUW/Ps/6/1fromsampleBAH−4,SteeplePasture,HaystackRange,Wyoming,Upper Carboniferous, Morrowan, in lingual−lateral, occlusal, lingual, labial, and labial−lateral views. F–G. Specimens OSU 50490 and 50491 from Gwi−3 and At−64 localities, Ohio, Upper Carboniferous, Conemaugh Group, Ames Limestone, in occlusal views. Scale bar 1 mm.