Cryopterygius kielanae, Tyborowski, 2016

Tyborowski, Daniel, 2016, A new ophthalmosaurid ichthyosaur from the Late Jurassic of Owadów-Brzezinki Quarry, Poland, Acta Palaeontologica Polonica 61 (4), pp. 791-803 : 793-801

Cryopterygius kielanae sp. nov.

Etymology: In honour to Zofia Kielan-Jaworowska (1925–2015), worldrenowned Polish researcher of Mesozoic mammals.

Holotype: GMUL 3579-81 , a fragment of the lower jaw, isolated teeth, fragments of pterygoid and quadrate, parts of the cervical, dorsal, and caudal vertebral column, most of the left pectoral girdle, right clavicle, right forefin, and left femur.

Type locality: Owadów-Brzezinki Quarry of Nordkalk GmbH, Sławno, vicinity of Tomaszów Mazowiecki (Central Poland); 51°22’34.53” N, 20°08’07.86” E.

Type horizon: Upper Jurassic (the uppermost Lower Tithonian = Middle Volgian), the lower part of the Kcynia Formation, the Sławno Limestone Member.

Diagnosis.—Medium size ophthalmosaurid ichthyosaur (estimated 3.5–4 m of total body length; based on comparisons of pectoral girdle and forefin size in other more complete ophthalmosaurids; the humerus and scapula are similar in size to those of Janusaurus lundi , which is estimated to be a medium-sized species), and is smaller in length than type species. Absence of a deep and wide ventral groove on the quadrate articular condyle (quadrate articular condyle divided by a deep and wide groove in Ophthalmosaurus icenicus , Sveltonectes insolitus , Acamptonectes densus , and Platypterygius australis ). Humerus with tall and prominent dorsal process located in the middle of the dorsal surface of the bone, rather than less prominent dorsal process located at the posterior margin of the dorsal surface of the bone in C. kristiansenae . Humerus with prominent deltopectoral crest, rather than very weakly developed deltopectoral crest in C. kristiansenae (relatively low dorsal process and deltopectoral crest in Ophthalmosaurus icenicus , Aegirosaurus leptospondylus , and Caypullisaurus bonapartei ). Humerus withtwodistalfacets(threedistalfacetsin Ophthalmosaurus icenicus , Brachypterygius extremus , Caypullisaurus bonapartei , Undorosaurus gorodischensis , Aegirosaurus leptospondylus , Janusaurus lundi , and Acamptonectes densus humeri). Proximal and distal ends of the femur anteroposteriorly broader in C. kielanae than in C. kristiansenae (relatively narrower femur in Ophthalmosaurus icenicus and Janusaurus lundi ).

Description.— Skull: The skull bones of Cryopterygius kielanae are represented by the right pterygoid, left quadrate and part of the lower jaw.

Pterygoid: The pterygoid bone is rectangular and is anteriorly and posteriorly incomplete ( Fig. 2A ). The posterior part of the pterygoid is thickened and forms short trigonal processes. The medial part of the dorsal surface of the bone is flat. The bone forms the medial edge of the interpterygoid vacuity. The maximum preserved anteroposterior length of the pterygoid is 128 mm.

Quadrate: As in other ophthalmosaurids the quadrate is a concentric, lunate-shape bone, it may be that more than half of the dorsal quadrate is missing ( Fig. 2B ). The occipital lamella is broken. The ventral part of the quadrate forms a wide articular condyle. The condyle is prominent and convex ventrally. The articular condyle has no deep and wide groove. The maximum mediolateral width of the articular surface of the condyle is 64 mm. The dorsal part of the quadrate is the thinnest part.

Mandible: The preserved part of the lower jaw is the posterior part of right ramus. The jaw fragment is anteriorly and posteriorly incomplete. The maximum length of the preserved part of the lower jaw is 245 mm. The maximum height of the preserved fragment of the lower jaw is 66 mm. A fragment of the lower jaw consists of a dentary bone and surangular bone ( Fig. 3 ). On the upper edge of the dentary bone, a longitudinal dentary groove 16 mm deep is present. This groove extends along the entire preserved portion of the lower jaw. The width of the dental groove is 26 mm. Inside the groove the tooth impressions are visible ( Fig. 3A ). The tooth impressions are oval in shape. The diameter of the impressions is 10 mm. All of the tooth impressions are located on the lingual wall of the dental groove. The maximum length of the surangular preserved fragment is 126 mm. A portion of the lateral surangular is visible at the anterior part of the jaw fragment. The distinguishing features of the surangular are lacking. The fossa surangularis appears well developed.

Dentition: Nine isolated teeth belonging to C. kielanae were found. The teeth were found in the vicinity of the preserved lower jaw fragment. Only one is preserved complete (root and crown; Fig. 4 ). Most of the teeth are preserved in the form of roots with broken crowns. The isolated crowns are also present. The complete tooth measures 32 mm in apicobasal length. The root measured 21 mm in length. The length of the crown is 11 mm. The crowns are conical and robust. All the teeth are curved lingually and nearly circular in cross section. There is no indication of prominent carinae. Crowns have ornamentation in the form of gentle apicobasal grooves.

Axial skeleton: Forty-two vertebrae are preserved in the holotype of C. kielanae . These vertebrae are preserved as the isolated centra ( Fig. 5 ). Four neural arches from the mid-dorsal region are also preserved. None of the neural arches are fused to the centra or with its neighbour. One of them has preserved the neural spine. Given that the typical vertebral count of ichthyosaurs is 90–100 ( McGowan and Motani 2003), the C. kielanae holotype includes about onehalf of the vertebral column. The specimen includes: 4 cervical vertebrae (including atlas-axis complex), 11 dorsal vertebrae and 27 caudal vertebrae.

Atlas-axis complex: The atlas-axis complex is completely fused together ( Fig. 5A ). There is a sutural boundary between the atlas centrum and axis centrum. The atlas centrum is longer anteroposteriorly than the axis centrum ( Table 1). The diapophyses (dorsal rib facet) of the atlas centrum and axis centrum cannot be discerned. A single apophysis, probably parapophysis (ventral rib facet) of the atlas centrum is visible in the anterior half of the atlas. The parapophysis of the axis centrum is visible at the posterior edge of the atlas-axis complex. All of the atlas-axis complex parapophyses are visible in the mid-height of the centra. The floor of the neural canal of the atlas-axis complex is 12 mm wide in the anterior edge of the atlas centra and 24 mm wide in the posterior edge of the axis centra.

Cervical vertebrae: All of the cervical centra are dorsoventrally taller than anteroposteriorly long, and they are as laterally wide as dorsoventrally high ( Fig. 5B ). The diapophysis and parapophysis are visible at the anterior edge of the centra. The diapophyses are confluent with the facets for the neural arches anteriorly on the top of the centra. All of the cervical centra parapophyses are located in the mid-height of the centra. The floor of the neural canal of the cervical centra is 25 mm wide.

Dorsal vertebrae: Passing from the anterior to the posterior regions of the dorsal backbone, centra tend to increase in size in all dimensions ( Fig. 5C ). In all dorsal centra the two rib facets are visible. The diapophyses and parapophyses from the anterior dorsal centra are dorsally located. The diapophyses from the anterior dorsal centra are still confluent with the facets for the neural arches. The diapophyses and parapophyses become situated more ventrally on centra towards the posterior of the dorsal region. The diapophyses on centra from the posterior part of the dorsal region are losing their contact with the facets for the neural arches. Also, the diapophyses from this region becomes reduced. The floor of the neural canal of the dorsal centra is 20 mm in wide.

Atlas centrum anteroposterior length 26 Axis centrum anteroposterior length 11 Cervical centra anteroposterior length 24 Smallest dorsal centrum anteroposterior length 24 Largest dorsal centrum anteroposterior length 28 Smallest caudal centrum anteroposterior length 8 Largest caudal centrum anteroposterior length 25 Scapula maximum proximodistal length 193 Scapula maximum anteroposterior width, proximal blade 78 Scapula maximum anteroposterior width, distal blade 34 Scapula, coracoid facet length 20 Scapula, glenoid facet length 40 Humerus maximum proximodistal length 118 Humerus maximum anteroposterior width, proximal end 62 Humerus maximum heigh, proximal end 65 Humerus maximum anteroposterior width, distal end 83 Humerus maximum heigh, distal end 41 Humerus minimum anteroposterior width, midshaft 50 Radius maximum proximodistal length 42 Ulna maximum proximodistal length 50 Femur maximum proximodistal length 76 Femur maximum anteroposterior width, proximal end 42 Femur maximum anteroposterior width, distal end 57 Femur minimum anteroposterior width, midshaft 36

Caudal vertebrae: Twenty-seven caudal vertebrae of C. kielanae are preserved ( Fig. 5D–F ), fifteen of which are preflexural vertebrae; twelve of them are postflexural vertebrae. The preflexural centra of C. kielanae are the largest of all the vertebral centra ( Table 1). The postflexural centra are laterally compressed and have a characteristically oval shape in anterior and posterior views. All of the preflexural centra have only one rib facet visible, probably the parapophysis. No rib facets are present in postflexural centra. The floor of the neural canal of the preflexural centra is 15 mm in wide. The floor of the neural canal of the postflexural centra is 7 mm in wide. The apical centra are not preserved.

Neural arches: Only five neural arches from the mid-dorsal region are preserved. The neural spines are present in two of these but the apical part of the one spine is eroded. One of the preserved neural spines has a V-shaped apical notch. However, the specimen was found in the other layer than the rest of the skeleton and cannot determine whether it belongs to that individual. Height of the neural arches measured from base of the pedicel at the neurocentral boundary to the midpoint of the spine along the lateral surface is 57 mm.

Ribs: The preserved ribs of the C. kielanae are very disarticulated. All are broken. Some are figure of 8 shaped in cross section and taper gradually to their distal ends. Some of the rib has bite marks and small grooves suggesting post-mortem activity of the scavengers.

Pectoral girdle: The pectoral girdle of Cryopterygius kielanae is better known from the left side, which includes nearly complete scapula and part of the clavicle. On the right side of the pectoral girdle only a part of the coracoid and clavicle are preserved.

Scapula: The scapula comprises a proximal blade that is anteroposteriorly expanded, and a narrow distal blade ( Fig. 6A ). The articular surface of the proximal blade includes an anterior, non-articular surface, the coracoid facet and the glenoid facet. The anterior, non-articular surface of the proximal blade supports the acromial process. The coracoid facet is relatively thin compared to the glenoid facet ( Table 1) and anterior, non-articular surface and is also shorter than the glenoid facet. The acromial process is poorly preserved, being incomplete dorsally. The proximolateral surface of the scapula has a broad concavity with forms approximately one-third of the total scapula length. The acromial process forms the anterior margin of this concavity. The distal blade is broken ventrally. The posterior margin of the distal blade is incomplete.

Coracoid: The right coracoid is not well preserved ( Fig. 6B ). The preserved part is from the intercoracoid facet region. The maximum mediolateral width of the preserved part of the coracoid is 116 mm. Length of intercoracoid facet is 103 mm. The intercoracoid facet probably forms the anterior half of the medial margin.

Clavicles: All preserved fragments of the left clavicle measure 80 mm in length. The left clavicle is broken from proximal and distal edge. The right clavicle is better preserved but is also anteriorly and posteriorly broken. The maximum length of the right clavicle is 152 mm. The bones are gently curved dorsally and posteriorly. The right clavicle has a facet for the scapula and the visceral surface of the bone is gently dented.

Forefin: The morphology of the Cryopterygius kielanae forefins is best understood from the right forefin, which includes a complete humerus, complete radius and ulna, and most of the metacarpals and phalanges ( Fig. 7). Most of them were found as disarticulated elements. The forefin is relatively small compared to total body length of C. kielanae . The length of the preserved part of the forefin is 300 mm, although distalmost phalanges are missing so the estimated total length of the forefin is 350 mm.

Humerus: The distal end of the humerus is wider than proximal end in maximum anteroposterior width ( Fig. 8 ). The anteroposterior width and dorsoventral height of the humerus proximal articular surface are nearly identical. The proximal articular surface is very irregular, suggesting a considerable investment in articular cartilage. The distal end of the humerus is anteroposteriorly longer ( Table 1) than dorsoventrally high. The dorsal process is broken but still more prominent than the deltopectoral crest ( McGowan and Motani 2003). The dorsal process is situated on the proximal half of the bone and it measures approximately 50 mm long and maximum 20 mm wide. It arises near the posterodorsal surface, and ends suddenly by the midpoint of the shaft ( Fig. 8 ). The deltopectoral crest is also prominent but is smaller than the dorsal process. The deltopectoral crest is situated ventrally on the proximal half of the humerus and is located at the anterior margin of the bone. The humerus has only two large distal facets for the radius and ulna. The radial facet is smaller than the ulnar facet. Anteroposterior length of the radial facet is 45 mm. Anteroposterior length of the ulnar facet is 52 mm. The facet for a preaxial accessory element is absent. Probably a preaxial accessory element does not directly articulate to the humerus. The radial and ulnar facets meet at an angle of 60°, looking from the dorsal view.

Zeugopodium and autopodium: The radius and ulna are the two largest bones anteriorly and posteriorly located. The posterior articular surface of both elements is gently rounded. Both bones are polygonal. All of them are broader than long. The radius is slightly smaller than the ulna ( Table 1; Fig. 7). The anterior surface of the radius is curved and covered with small hummocks. The preaxial accessory element, radiale, intermedium, ulnare, distal carpals, metacarpals and phalanges are found as disarticulated elements in one layer. They were identified on the basis of Motani’s (1999) criteria. The preaxial accessory element is teardrop-shaped. It is anteroposteriorly broadest and dorsoventrally thinnest proximally. The anterior margin of the preaxial accessory element is thinner than the posterior margin. It bears a posterior facet for the radius. The radiale, intermedium and ulnare are polygonal and broader than long. They are approximately of the same size. The interpretation of homology of the distal carpals and metacarpals is ambiguous. Probably the metacarpal V contacts the ulnare and the distal carpal 4. The proximal phalanges are rectangular and pentagonal.

Hindfin: The hindfin bones of C. kielanae are represented only by the left femur ( Maxwell et al. 2012; Fig. 9 ). The distal end of the femur is wider than the proximal end ( Table 1). Anteriorly, the femur is broad, but tapers posteriorly to a thin, blade-like posterior margin. The proximal articular surface is undulating and very irregular, and bears prominent hummocks, suggesting a considerable investment in articular cartilage just like on the humerus. From the anterior view and posterior view the femur is nearly symmetrical. The dorsal surface of the femur bears a low and rounded dorsal process which is located close to the anterior margin of the bone. The ventral surface bears a low, ventral process that is situated close to the anterior margin of the femur. Distally, the femur bears only two articular facets for tibia and fibula. The fibular facet is much longer than the tibial facet. Length of the tibial facet is 23 mm. Length of the fibular facet is 35 mm. Tibial and fibular facets are triangular-shaped in distal view. In dorsal view, the tibial and fibular facets of the femur meet at an angle of approximately 30°.

Remarks.— Cryopterygius kielanae holotype bones were found in a locality where marine reptile bones are frequently found ( Tyborowski et al. 2016). The similar size and association of the bones in one sector of the quarry suggest that they belong to a single individual. Ophthalmosauridae are known from the Jurassic and Cretaceous, and include taxa such as Ophthalmosaurus ( Kirton 1983) , Aegirosaurus ( Bardet and Fernandez 2000) , Nannopterygius ( Hulke 1871) , Caypullisaurus ( Fernandez 1997) , Janusaurus ( Roberts et al. 2014) , Cryopterygius (Druckenmiller et al. 2012) , Platypterygius ( Maxwell and Kear 2010) , Acamptonectes ( Fischer et al. 2012) , Arthropterygius (Maxwell 2010) , and Undorosaurus ( Efimov 1999) . Clearly, C. kielanae is a member of Ophthalmosauridae . Like the rest of the members of this group it has a preaxial accessory element in the forefin zeugopodium ( McGowan and Motani 2003). The presence of a quadrate in the shape of ear is also a feature of most ophthalmosaurids ( Fischer et al. 2014). As skull fragments are mostly incomplete, it is difficult to compare them with the bones of other ophthalmosaurids. The quadrate has a stapedial facet, although it is not as well developed as in other taxa such as Acamptonectes ( Fischer et al. 2012) . The articular condyle appears prominent and convex ventrally, unlike many ophthalmosaurids ( Ophthalmosaurus icenicus , Sveltonectes insolitus , Acamptonectes densus , and Platypterygius australis ), where the condyle is divided by a wide groove ( Kirton 1983; Kear 2005; Fischer et al. 2011, 2012). The fossa surangularis is present on the surangular bone and appears well developed unlike in Sveltonectes insolitus ( Fischer et al. 2011) .

A dorsal process 20 mm B humerus ulna preaxial accessory intermedium element ulnare radiale 2–4 metacarpals ii–v distal carpals

radius

The pectoral girdle of the ophthalmosaurids has a wide range of intraspecific variations ( Maxwell and Druckenmiller 2011), which makes comparing Cryopterygius kielanae to other ophthalmosaurids problematic. However, some comparisons can be made. The scapula of C. kielanae is generally similar to that of Undorosaurus ( Efimov 1999) and C. kristiansenae (Druckenmiller et al. 2012) . The distal blade of the scapula in C. kielanae is relatively shorter than that of Caypullisaurus . The base of the acromial process is not so prominent such as Acamptonectes ( Fischer et al. 2012) . The clavicles are similar to Janusaurus lundi ( Roberts et al. 2014) and Ophthalmosaurus icenicus ( Kirton 1983) . Both clavicles are curved dorsally and posteriorly. The visceral surface of the right clavicle is dented, as in Janusaurus lundi ( Roberts et al. 2014) .

Certainly, the forefin of C. kielanae is the most diagnostic part of the skeleton. The humerus has only two distal facets for radius and ulna. Most of the ophthalmosaurids have three distal facets: Ophthalmosaurus icenicus ( Kirton 1983) , Aegirosaurus leptospondylus ( Bardet and Fernandez 2000) , Caypullisaurus bonapartei ( Fernandez 1997) , Brachypterygius extremus ( Boulenger 1904) , Undorosaurus gorodischensis ( Efimov 1999) , Janusaurus lundi ( Roberts et al. 2014) , Acamptonectes densus ( Fischer et al. 2012) , and Arthropterygius (Maxwell 2010) . The ophthalmosaurids with only two distal facets are Cryopterygius kristiansenae (three distal facets on the right humerus; Druckenmiller et al. 2012), Nannopterygius enthekiodon ( Hulke 1871) , Sveltonectes Fischer et al. 2011 ), and many species of Platypterygius McGowan and Motani 2003 ). The forefin of Platypterygius americanus from the Lower Cretaceous is similar to C. kielanae ( Maxwell and Kear 2010) . The proximal phalanges of Platypterygius americanus and Cryopterygius kielanae are rectangular ( Maxwell and Kear 2010). The humerus of C.

kielanae is relatively small compared to Platypterygius hercynicus ( Kolb and Sander 2009) and Undorosaurus gorodischensis ( Efimov 1999) . The humeri of Cryopterygius kristiansenae and Nannopterygius enthekiodon are also reduced ( Hulke 1871; Druckenmiller et al. 2012). Little is known about the Nannopterygius forefin and virtually nothing about its humeral and preaxial accessory element morphology. Aegirosaurus leptospondylus differs from the C. kielanae by the presence of three distal facets on the humerus ( Bardet and Fernandez 2000). Aegirosaurus and Brachypterygius share a humerus-intermedium contact ( Bardet and Fernandez 2000). The Cryopterygius kielanae intermedium has no contact with the humerus. Janusaurus also has three distal facets on the humerus ( Roberts et al. 2014) and the anterior facet is the preaxial accessory element facet. C. kielanae also has a preaxial accessory element, but there is no preaxial accessory element facet on the humerus. The femur of C. kielanae , which has only two distal facets for both the tibia and the fibula, differs from the three-facet forms of Platypterygius australis , Platypterygius americanus , and Paraophthalmosaurus kabanovi ( Maxwell and Kear 2010; Zammit et al. 2010; Arkhangelsky and Zverkov 2014).

The holotype of C. kristiansenae and the new ophthalmosaurid C. kielanae from the Owadów-Brzezinki Quarry share the following characters: (i) relatively short (proximodistally) humerus (compared to animal body) with only two distal facets for radius and ulna (three facets on the right humerus in C. kristiansenae ), (ii) proximal phalanges rectangular or pentagonal, (iii) femur anteroposteriorly broad with only two distal facets for tibia and fibula, (iv) proximolateral surface of the scapula with a broad concavity, (v) neural arches with V-shaped apical notch in the neural spines (however, the only specimen found with this feature in Owadów-Brzezinki Quarry may not belong to this individual). Nevertheless C. kielane differs from C. kristiansenae in several aspects: (i) ulnar facet larger than the radial facet in C. kielanae ; radial facet and ulnar facet equal in anteroposterior length in C. kristiansenae , (ii) tall and prominent dorsal process on C. kielanae humerus; low dorsal process on C. kristiansenae humerus, (iii) dorsal process located in the middle of the dorsal surface of the humerus in C. kielanae ; dorsal process located at the posterior margin of the dorsal surface of the humerus in C. kristiansenae , (iv) prominent deltopectoral crest on C. kielanae humerus; very weakly developed deltopectoral crest on C. kristiansenae humerus, (v) femur broader in C. kielanae than in C. kristiansenae , (vi) fibular facet larger than the tibial facet in C. kielanae ; tibial facet and fibular facet equal in anteroposterior length in C. kristiansenae , (vii) C. kielanae body significantly smaller than C. kristiansenae body ( C. kielanae estimated 3.5–4 m total body length; C. kristiansenae estimated 5.5 m total body length).

The specimen is interpreted to be an adult, based on the articular surface of the humeral head which is convex, concavity of the distal facets, the smoothness of the humeral shaft and the advanced ossification of the forefin elements ( Johnson 1977; Kear and Zammit 2014). Also the dorsal ribs with thick cortical bone are interpreted as an ontogenetic adult trait ( Kear and Zammit 2014).

Stratigraphic and geographic range.— Type locality and horizon only.

Figures

Fig. 2. Morphology of skull bones of ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. (GMUL 3579-81, holotype) from the Late Jurassic of Owadów-Brzezinki Quarry. A. Left pterygoid in ventral (A1) and dorsal (A2) views. B. Left quadrate in lateral (B1), anterior (B2), and medial (B3) views.

Fig. 3. Rostrum fragment of ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. (GMUL 3579-81, holotype) from the Late Jurassic of Owadów- Brzezinki Quarry; in “dental/apical” (A) and right-lateral (B) views.

Fig. 4. Ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. GMUL 3579-81, holotype) from the Late Jurassic of Owadów-Brzezinki Quarry; tooth in labial (A) and anterior (B) views.

Fig. 5. Morphology of isolated centra of ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. (GMUL 3579-81, holotype) from the Late Jurassic of Owadów-Brzezinki Quarry. Atlas-axis complex (A), cervical (B), dorsal (C), preflexural caudal (D), and postflexural caudal (E) centra, preflexural caudal spine (F); in anterior (A1–E1) and left-lateral (A2–E2, F) views.

Fig. 6. Morphology of scapula and coracoid of ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. (GMUL 3579-81, holotype) from the Late Jurassic of Owadów-Brzezinki Quarry. A. Left scapula in lateral (A1) and medial (A2) views. B. Right coracoid in lateral (B1) and articular (B2) views.

Fig. 8. Right humerus of ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. (GMUL 3579-81, holotype) from the Late Jurassic of Owadów-Brzezinki Quarry; in dorsal (A), ventral (B), anterior (C), and posterior (D) views.

Fig. 9. Left femur of ophthalmosaurid ichthyosaur Cryopterygius kielanae sp. nov. (GMUL 3579-81, holotype) from the Late Jurassic of Owadów- Brzezinki Quarry; in dorsal (A), posterior (B), anterior (C), proximal (D), and distal (E) views.