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New plesiosaurian specimens (Reptilia, Plesiosauria) from the Upper Cretaceous (Turonian) of Goulmima (Southern Morocco)
Abstract
Two new plesiosaurian specimens coming from lower Turonian deposits of Goulmima in Morocco are described. The three-dimensional digital reconstructions of both specimens provide details about their skull roof, mandible and atlas-axis complex. In addition, computed tomography allows to reconstruct their braincase, which is a part of the skull poorly known among plesiosaurians due to either poor preservation and/or insufficient preparation, but that offers a large number of characters used in phylogenetical analyses. After descriptions and comparisons, the two specimens D1-8213 and MNHN F-GOU14 are assigned to Libonectes morgani and to an undetermined Polycotylidae, respectively. The presence of the North American taxon Libonectes morgani in the deposits of Goulmima confirms a trans-Atlantic faunal connectivity at that time and that Elasmosauridae were able to exploit the open marine environment for dispersion. Polycotylids have already been described from Goulmima; however, the typical preservation of these specimens in nodules prevented their preparation and the access to their internal anatomy. Here, the use of X-ray computed tomography shows the strong interest to use such a technique and provide new anatomical details.
... Vertebrate remains are very abundant in Cretaceous deposits of southern and central Morocco (e.g. Cavin et al., 2001Cavin et al., , 2010Angst and Bardet, 2015;Vullo et al., 2016Vullo et al., , 2017Allemand et al., 2018). In this region, excavation activities by local people have particularly intensified during the past two decades to collect Cretaceous fossils for commercial purposes, but although numerous finds were discovered by these commercial activities, associated data on the original sedimentology, stratigraphy and provenience of the specimens, however, often are lacking (Cavin et al., 2010). ...
... Local people commonly excavate various localities in the Goulmima area (e.g. the villages of Tadirhoust and Asfla; see white asterisk in Fig. 2), searching for macrofossils, such as exceptionally preserved vertebrate remains usually embedded in calcareous nodules (e.g. Bardet et al., 2003a, b;Cavin et al., 2010;Claeson et al., 2013;Angst and Bardet, 2015;Allemand et al., 2018;Cooper and Martill, 2020;Villalobos-Segura et al., 2021). In particular, a sequence of alternating facies succession consisting of fossiliferous packstones, chalky marls, cherts and vertebrate-bearing nodular horizons belonging to the Asfla Member ( Fig. 2B) of the Akrabou Fm of the Asfla area are targeted for vertebrate fossils (e.g. ...
... mosasauroids and plesiosaurs) and, more rarely, elasmobranchs (e.g. Bardet et al., 2003a, b;Kennedy et al., 2008;Cavin et al., 2010;Claeson et al., 2013;Angst and Bardet, 2015;Gale et al., 2017;Meister et al., 2017;Allemand et al., 2018;Villalobos-Segura et al., 2019Cooper and Martill, 2020). Additionally, the limestones of the Akrabou Fm include shell beds, with a low-diversified bivalve assemblage, and stromatolites in various horizons (Kennedy et al., 2008;Cooper and Martill, 2020). ...
The first articulated dentition of †Ptychodus from Africa is described herein. The specimen, likely coming from the Turonian of the Asfla area (Goulmima region, southeastern Morocco), exhibits a well-preserved lower dental plate of a second-level predator. A new species, †P. maghrebianus sp. nov., is erected herein based on this durophagous dentition characterised by imbricated cuspidate teeth. We employed for the first time in †Ptychodus multiple quantitative analyses and statistical parametric and non-parametric tests to process biometrical data taken from articulated, associated and isolated teeth. The quantitative approach (morphospace analysis) is exploited herein to support the traditional taxonomic identification (qualitative examination) of †P. maghrebianus sp. nov. and to separate it from the similar cuspidate species, †P. mortoni. Morphospace reconstructions confirm a marked lower dental heterodonty (mesio-distal patterns) for both species. The analysis protocol employed here also allows assigning indeterminate teeth as belonging to †P. mortoni. The reconstruction of the entire lower dental plate of †P. maghrebianus sp. nov. shows a cuspidate dentition probably able to reduce tooth damages when crushing thin-shelled prey. Both dental morphologies and tooth wear patterns suggest a peculiar food processing and a diet mainly consisting of bivalves, decapods and small fish for this durophagous predator. Trophic reconstructions of the Turonian ichthyofauna inhabiting the middle to outer ramp environment of the Asfla area emphasize that †P. maghrebianus sp. nov. and the batoid †Tingitanius most likely represented second-level consumers, whereas the sclerorhynchiforms †Asflapristis and †Ptychotrygon represented third-level predators. Top positions within the food web were occupied by larger predaceous elasmobranchs (e.g., †Squalicorax).
... The vomer contributes to the anterior and medial border of the internal naris, while the lateral margin of the internal naris is bordered by a palatal extension from the maxilla (Fig 6). In ventral view, the vomer does not have a ventral ridge, as in Libonectes morgani (D1-8213) [71]. The vomer extends posteriorly beyond the internal naris and is not separated medially by the pterygoids (Fig 6), as in Lagenanectes richterae [11], and the aristonectines Morturneria seymourensis [67,68] and Aristonectes parvidens [70]. ...
... Lateral to the interpterygoid fenestra, the pterygoid is broad in being nearly the same width mediolaterally as the interpterygoid fenestra and forms a trough along the ventral surface (Figs 6 and 9E-9G). A trough or excavation along the ventral surface is a common characteristic among elasmosaurids [10,13,41,71,73,74]. ...
... In Thalassomedon haningtoni, the epipterygoid exhibits a more smoothly convex distal margin (S2 Fig). Libonectes morgani and Tuarangisaurus keyesi both exhibit epipterygoids that are similar to MGUAN PA278 in being mediolaterally thin elements with a triangular outline in lateral view and a distal margin oriented anterodorsally [49,63,71,77]. ...
We report a new specimen of the plesiosaur Cardiocorax mukulu that includes the most complete plesiosaur skull from sub-Saharan Africa. The well-preserved three-dimensional nature of the skull offers rare insight into the cranial anatomy of elasmosaurid plesiosaurians. The new specimen of Cardiocorax mukulu was recovered from Bentiaba, Namibe Province in Angola, approximately three meters above the holotype. The new specimen also includes an atlas-axis complex, seventeen postaxial cervical vertebrae, partial ribs, a femur, and limb elements. It is identified as Cardiocorax mukulu based on an apomorphy shared with the holotype where the cervical neural spine is approximately as long anteroposteriorly as the centrum and exhibits a sinusoidal anterior margin. The new specimen is nearly identical to the holotype and previously referred material in all other aspects. Cardiocorax mukulu is returned in an early-branching or intermediate position in Elasmosauridae in four out of the six of our phylogenetic analyses. Cardiocorax mukulu lacks the elongated cervical vertebrae that is characteristic of the extremely long-necked elasmosaurines, and the broad skull with and a high number of maxillary teeth (28–40) which is characteristic of Aristonectinae. Currently, the most parsimonious explanation concerning elasmosaurid evolutionary relationships, is that Cardiocorax mukulu represents an older lineage of elasmosaurids in the Maastrichtian.
... MPEF-PV 11545 is referred to Kawanectes lafquenianum because of the combination of three features: 1) high and triangular coronoid process, 2) elongated cervical centra and 3) laterally projected caudal parapophyses. Feature 1) is shared among euelasmosaurids only by Terminonatator ponteixensis Sato, 2003, Tuarangisaurus keyesi Wiffen, Moisley, 1986, Nakonanectes bradti and Libonectes morgani (Welles) Carpenter, 1997(Sato, 2003Serratos et al., 2017;Allemand et al., 2017Allemand et al., , 2018. However, Terminonatator ponteixensis lacks laterally projected caudal parapophyses and additionally the ilium of T. ponteixensis shows a fanshaped dorsal end that differs from K. lafquenianum (Sato, 2003: fig. ...
... 6; Allemand et al., 2018: fig 6). However, in all specimens of Libonectes morgani the parasphenoid keel extends caudally and shows a posterior pterygoid symphysis, differing from the features of MPEF-PV 11545 (Carpenter, 1997;Allemand et al., 2017Allemand et al., , 2018. ...
... The occipital condyle in posterior view is wider than high (W/H > 1.1) in Alexandronectes zealandiensis and Morturrneria seymourensis O'Keefe et al., 2017). However, the occipital condyle is higher than wide or subcircular in K. lafquenianum, as in Callawaysaurus colombiensis; Libonectes morgani and Nakonanectes bradti and the SGU 251/1 (Allemand et al., 2017(Allemand et al., , 2018Sachs et al., 2017;Serratos et al., 2017;Welles, 1962;Zverkov et al., 2018;J.P.O'G pers. obs.). ...
Elasmosaurids are a cosmopolitan group of plesiosaurians that radiated during the Late Cretaceous. A new specimen of the small sized elasmosaurid Kawanectes lafquenianum is described here. New features of the basicranium and palate are added: basioccipital tubers with distal end deeply excavated, basioccipital ventral flat plate below occipital condyle, absence of posterior interpterygoid symphysis, parasphenoid extended caudally to the posterior margin of basioccipital condyle, craniocaudally short ventral keel of parasphenoid. Differences recorded between the specimens referred to K. lafquenianum (ilium shape, relative humerus to femur size and sacral centrum proportions) are described. Different explanations of these differences are discussed, concluding that sexual dimorphism is the most plausible explanation.
... The basioccipitals of DMNS 1588 and UNSM 50132 (Fig. 6AeD) have hemispherical occipital condyles reminiscent of those in Callawayasaurus colombiensis (Welles, 1962), Libonectes morgani (Carpenter, 1997;Allemand et al., 2018), Lagenanectes richterae (Sachs et al., 2017a), and Nakonanectes bradti (Serratos et al., 2017), but unlike the massive, sub-quadrangular condylar profile characterising the aristonectine Alexandronectes zealandiensis 2AeE). Conspicuously, the condylar grooves of both DMNS 1588 and UNSM 50132 are truncated and incomplete dorsally, as reported in some other elasmosaurid remains (Kear, 2001;O'Gorman et al., 2018a). ...
... The basisphenoid is exposed laterally between the epipterygoid and prootic within in the temporal opening of UNSM 50132 ( Fig. 6E and F). It encloses an irregular opening with the prootic along its posterior edge that corresponds in position to the trigeminal foramen of Libonectes morgani (Carpenter, 1997;Allemand et al., 2017Allemand et al., , 2018. Part of the endocranial space above the sella turcica (compare with Allemand et al., 2018, p. 88, fig. ...
... 3B). The cultriform process is broken off anteriorly, but was keeled like those of other elasmosaurids (Welles, 1962;Carpenter, 1997;Sachs 2005aSachs , 2005bKear 2005aKear , 2005bKear , 2007O'Gorman et al., 2017;Serratos et al., 2017;Allemand et al., 2017Allemand et al., , 2018Sachs et al., 2017a;Zverkov et al., 2018), with the exception of aristonectines (Otero et al., 2014;O'Keefe et al., 2017). ...
Thalassomedon haningtoni is one of the most completely preserved elasmosaurid plesiosaurians described to date. Unlike most other elasmosaurid fossils, both the holotype and a second referred specimen — which were recovered from the middle Cenomanian Graneros Shale in the mid-western USA — are represented by intact skulls with articulated postcranial skeletons. Thalassomedon haningtoni thus constitutes an ideal ‘model elasmosaurid taxon’ that contributes significant character state data towards resolving contested relationships within the clade. Here, we present a detailed reassessment of the cranial osteology of T. haningtoni with the aim of evaluating its disputed species-level monophyly, together with its broader phylogenetic affinities. We identify several key diagnostic cranial traits including a sharply tapered premaxillary rostrum with a pronounced dorsomedian ridge that extends to the tip of the snout, a proportionately very small and rounded external bony nasal opening, and an anisodont functional dentition that incorporates a pair of enlarged ‘fangs’ in the second maxillary tooth position. Our phylogenetic analyses using first-hand scores unequivocally support classification of the Graneros Shale specimens as conspecific. Furthermore, consistent nesting with other North American elasmosaurid taxa suggests that T. haningtoni could evidence successive lineage divergences that took place within the Western Interior Seaway during the middle to latest Cretaceous.
... The distolabial enamel surfaces of RSU DGE 2019 RO MP-107 are smooth, but the mesiolabial surfaces bear fine, anastamosing apicobasal ridges that extend to the apex (Fig. 3G, H). At 11.5 mm in maximum basal diameter, RSU DGE 2019 RO MP-107 is stouter than the thin 'needle-like' teeth of aristonectine elasmosaurids (see Otero et al., 2014;O'Keefe et al., 2017), and otherwise resembles the more robust anisodont dentitions of non-aristonectines , such as the middle Cenomanian Thalassomedon haningtoni Welles, 1943(Sachs et al., 2021, and uppermost CenomanianeTuronian Libonectes morgani (Welles, 1949) from Colorado, Nebraska, and Texas, USA (Welles, 1943(Welles, , 1949Sachs and Kear, 2015), and Morocco (Buchy, 2005;Allemand et al., 2017Allemand et al., , 2018Allemand et al., , 2019. ...
... Like brachauchenine pliosaurids, elasmosaurids and polycotylids were geographically ubiquitous Late Cretaceous plesiosaurian clades, but with numerous CenomanianeTuronian records (including trans-Atlantic species ranges, e.g., Libonectes morgani: from European Russia to Western Europe (e.g., Persson, 1963;Milner, 1987;Bardet and Godefroit, 1995;Storrs et al., 2000;Kear et al., 2014;Sachs et al., 2016Sachs et al., , 2018, North Africa (e.g., Bardet et al., 2003a;Allemand et al., 2017;Allemand et al., 2018;Fischer et al., 2018;Allemand et al., 2019), and North America (e.g., Carpenter, 1996Carpenter, , 1997Carpenter, , 1999Storrs, 1999;Sachs and Kear, 2015;Sachs et al., 2021). Similarly, Late Cretaceous ophthalmosaurid ichthyosaurians were globally distributed, and apparently diversified within the epicontinental seas covering what is now the Russian Platform prior to their final extinction at the end of the Cenomanian . ...
During the Cenomanian–Turonian transition (∼94 Ma), what is today Central Russia formed part of the northern epicontinental margin of the Tethys Ocean. Diverse marine vertebrate faunas inhabited these palaeoenvironments, but their fossils are incompletely documented. Here, we report the discovery of marine reptile remains, recovered together with pterosaur, chondrichthyan, and actinopterygian fish material from a basal-most glauconitic sand and gravel layer of the Dmitrov Formation. These strata are exposed in an active quarry near the village of Malyy Prolom in the Shatsky District of Ryazan Oblast, Central Russia. The Dmitrov Formation deposits are middle–upper Santonian, but unconformably contact the underlying lower–middle Cenomanian Yakhroma Formation via a condensed boundary horizon that contains the vertebrate fossils with bivalve shell fragments and siliceous and phosphatic clasts. Such sedimentary characteristics indicate a high-energy shoreface setting where the vertebrate teeth and bones were likely reworked during cyclical regressions commencing in the latest Cenomanian–early Turonian. Time-averaging is also evidenced by the mixed occurrences of brachauchenine pliosaurids, elasmosaurid and polycotylid plesiosauroids, ophthalmosaurid ichthyosaurians similar to Pervushovisaurus, and a possible yaguarasaurine mosasauroid. These taxa are typical of Cenomanian–Turonian assemblages from across the northern peri-Tethys, and represent components of what were probably palaeobiogeographically widespread marine reptile faunas.
... Plesiosaurs are known in Africa by leptocleidids in the Valanginian of South Africa (Andrews, 1911;Cruickshank, 1997), pliosaurids (Angst and Bardet, 2015) and polycotylids Buchy et al., 2005;Allemand et al., 2018Allemand et al., , 2019 in the Turonian of Morocco. As far as they are concerned, African elasmosaurids are known in Morocco, both in the Turonian (Buchy, 2006;Allemand et al., 2017Allemand et al., , 2018Allemand et al., , 2019 and the Maastrichtian (Vincent et al. 2011(Vincent et al. , 2013, as well as in the Maastrichtian of Angola (Araújo et al., 2015) and the Maastrichtian of Egypt (Werner and Bardet, 1996) (see Vincent et al., 2011 for details). ...
... Plesiosaurs are known in Africa by leptocleidids in the Valanginian of South Africa (Andrews, 1911;Cruickshank, 1997), pliosaurids (Angst and Bardet, 2015) and polycotylids Buchy et al., 2005;Allemand et al., 2018Allemand et al., , 2019 in the Turonian of Morocco. As far as they are concerned, African elasmosaurids are known in Morocco, both in the Turonian (Buchy, 2006;Allemand et al., 2017Allemand et al., , 2018Allemand et al., , 2019 and the Maastrichtian (Vincent et al. 2011(Vincent et al. , 2013, as well as in the Maastrichtian of Angola (Araújo et al., 2015) and the Maastrichtian of Egypt (Werner and Bardet, 1996) (see Vincent et al., 2011 for details). ...
Twenty-two ammonite species are identified in the upper Albian Mortoniceras (Subschloenbachia) rostratum, Mortoniceras (Subschloenbachia) perinflatum and Stoliczkaia (Shumarinaia) africana Zones, and in the lower Cenomanian Mantelliceras mantelli Zone. The species Placenticeras Saadensis Thomas and Peron, 1890 is revised, including Engonoceras Thomasi Pervinquière, 1907, and is placed within the genus Hypengonoceras Spath, 1922. This accurate biostratigraphic framework allowed to evidence, at the Albian-Cenomanian transition (S. (S.) africana Zone), a significant sea level drop, responsible for emergence and erosion to the SE, and for deposition of a Lowstand wedge to the NW, fed by erosional channels on the shelf slope. Plesiosaur remains found in the upper Albian series (base of M. (S.) rostratum Zone) represent one of the few elasmosaurids known worldwide in the Albian, and the first plesiosaurian reported from Tunisia.
... The ichthyofauna is mainly composed of pelagic teleosts (Cavin, 1995;Cavin et al., 2010;Veysey et al., 2020), however pycnodontiforms and an araripichthyid also occur (Cavin, 1997;Cooper and Martill, 2020) alongside rarer chondrichthyans (Villalobos-Segura et al., 2019a;Amadori et al., 2022) (Table 1). Marine tetrapods include elasmosaurid and polycotylid plesiosaurs (Bardet et al., 2003a;Allemand et al., 2018), pliosaurs (Angst and Bardet, 2016), protostegid turtles (Cavin et al., 2010) and tethysaurs (Bardet et al., 2003b). Invertebrate faunas are restricted in the Asfla Member, but are more prevalent and diverse in the underlying and overlying beds, where there are abundances of cirripedes, bivalves, gastropods, scleractinian corals and trace fossils (Lebedel et al., 2015). ...
Ganoine-scaled fishes belonging to the superfamily Lepisosteoidea, more commonly known as gars, are an ancient lineage with origins in the Mesozoic, first appearing in the Kimmeridgian, Late Jurassic. The Mesozoic gar fossil record is patchy, mostly consisting of disarticulated remains, with only a few partially or mostly complete specimens being extremely rare. Extant gars typically occur in freshwater and brackish environments, with rare observations of a few species frequenting saline waters although little is known of their marine ancestors. Here we describe a new genus and species, Grandemarinus gherisensis gen. et sp. nov., an unusually short-snouted gar from the Upper Cretaceous (Turonian) Akrabou Formation of Morocco. The short-snouted cranial bauplan is superficially convergent with the Eocene freshwater genera Cuneatus and Masillosteus, although a phylogenetic analysis resolves the new gar as the sister taxon to the Lepisosteini (Oniichthys, Lepisosteus, Atractosteus), falling outside of Masillosteinae (Masillosteus, Cuneatus). Gars likely originated as fully marine fishes during the Late Jurassic, and during Early Cretaceous times successfully invaded freshwater ecosystems. The new gar described here is likely a late surviving member of this early marine lineage. The new lepisosteiform is the first complete gar described from a Cretaceous marine deposit; representing a vital clue to help decipher the early evolution and ecology of Lepisosteidae. The taphonomy of the specimen is discussed within the context of a fully marine carbonate Konservat Lagerstätte.
... Pterygoid-The stick-like quadrate process of the pterygoid observed in C. colombiensis and Libonectes morgani (Welles, 1962, Carpenter, 1997, Allemand et al., 2018O'Gorman et al., 2018) differs from the plate-like quadrate process of A. zealandiensis. A similar plate-like quadrate process of the pterygoid is recorded among other aristonectines: A. quiriqinensis and K. katiki . ...
The holotype specimen of Alexandronectes zealandiensis is analyzed using digital reconstruction based on CT scans. Additional information regarding internal anatomy or obscured details are added. Additional features include: ectopterygoid rhombic in shape with posterior end pointed, a feature shared only with Aristonectes quiriquinensis;
pterygoid shows a high dorsal crest located anteriorly and laterally to the level of the basipterygoid process; posterior margin of parabasisphenoid medially notched in ventral view and surrounding anteriorly and laterally a midline pit. Two canals for XII nerve are present in the right exoccipital-opisthothic and only one in the left one. Supraoccipital with two medially curved ridges on its posterior surface. Additionally, the presence of a stapes is described for the first time in an aristonectine elasmosaurid. The inner ear labyrinth is described and compared with that of other plesiosaurs, and the floccular recess (osseous correlate of the floccular lobe of the cerebellum) is described for first time among elasmosaurids. This feature is probably related to the presence of a long neck and with predatory behavior as the floccular lobe (housed in the floccular recess) stabilized the head via the cervical musculature, and stabilized the retinal image during rotational head movements.
... 2A), or high and triangular (Allemand et al. 2017, p. 9, fig. 6c, Allemand et al. 2018, p. 90, fig. 5). ...
O’Gorman, J.P. 27 November, 2019. First record of Kawanectes lafquenianum (Plesiosauria, Elasmosauridae) from the La Colonia Formation of Argentina, with comments on the mandibular morphology of elasmosaurids. Alcheringa XX, XX–XX. ISSN 0311-5518
The elasmosaurid plesiosaur Kawanectes lafquenianum is recorded from the upper Campanian–Maastrichtian levels of the La Colonia Formation in Argentina for the first time, thus extending the stratigraphical range of this taxon, which was previously recorded only from the geographically proximal Allen Formation. The new fossils are referrable to K. lafquenianum on the basis of the large posterodistal projection on the humerus supporting an articular facet for a proximal supernumerary ossification, the presence of a depression anterior to the main muscle scar on ventral surface of the humeral shaft, and a high humerus/femur length ratio (∼1.2). Novel diagnostic character states for K. lafquenianum include the presence of a high triangular and distally pointed coronoid process on the mandible, a mandibular symphysis that incorporates 2.5 alveolar spaces on each ramus, and a retroarticular process without dorsal or medial inflexion. Relatively low b/a ratio (measure of coronoid–glenoid cavity length/preglenoid length) could suggest a mechanical advantage toward fast jaw closure and weak bite forces. Comparisons with other elamosaurids this imply that Southern Hemisphere weddellonectian taxa, such as K. lafquenianum, Aristonectes parvidens and Kaiwhekea katiki, were possibly adapted for rapid snapping bites.
José Patricio O’Gorman [joseogorman@fcnym.unlp.edu.ar], División Paleontología Vertebrados, Museo de La Plata, Universidad Nacional de La Plata, Paseo del Bosque s/n., B1900FWA, La Plata, Argentina, CONICET (Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina), Buenos Aires, Argentina.
... Its pelvic girdle differs significantly from that of the Algora plesiosaur in having a pubis with convex anterior margin and sharp lateral cornu, and no pelvic bar though the specimen is adult. Eromangasaurus (see Kear, 2007) and Woolungasaurus (see Persson, 1960) from the Albian of Australia, Wapuskanectes from the Albian of Alberta (Canada) (Druckenmiller and Russell, 2006), as well as Libonectes from the Turonian of Texas (USA) and Morocco (see Sachs and Kear, 2017;Allemand et al., 2017a,b) do not preserve any pelvic girdle element so that comparisons remain impossible. Pending for more discoveries, the specimen of Algora is here referred to an indeter- minate Elasmosauridae. ...
Upper Cretaceous coastal marine deposits are widespread in the Southern Urals with a number of marine vertebrates previously reported from this region. However, previous studies on the vertebrate faunas in this region often lack detailed taxonomic descriptions and illustrations, rendering comparisons to other faunal assemblages difficult. A new diverse vertebrate assemblage comprising cartilaginous and bony fishes, as well as marine reptiles, is described here from the Orenburg region near Akkermanovka (Southern Urals, Russia). Thirty five taxa are identified, including three holocephalans (Elasmodus sp., Ischyodus yanshini, Chimaeroid indet.), two hybodontiform sharks (Meristodonoides sp., cf. Polyacrodus sp.), 17 neoselachians (Paraorthacodus cf. andersoni, Paraorthacodus sp., Synechodus sp., Cederstroemia nilsi, Acrolamna acuminata, Archaeolamna ex gr. kopingensis, Cretalamna sarcoportheta, Cretoxyrhina mantelli, Eostriatolamia segedini, E. venusta, Hispidaspis horridus, Hispidaspis cf. gigas, Pseudocorax laevis, Pseudoscapanorhynchus compressidens, Scapanorhynchus rhaphiodon, Squalicorax kaupi, Ptychodus rugosus), a holostean (Lepisosteidae indet.), nine teleosts (Protosphyraena sp., Saurodontidae indet., cf. Pachyrhizodus sp., Pachyrhizodontidae indet., Enchodus petrosus, E. ferox, E. cf. gladiolus, E. spp., Alepisauroidei indet.), two plesiosaurs (Polycotylidae indet., Plesiosauria indet.), and one mosasaurid (Tylosaurinae indet.). Based on the faunal assemblage, a Santonian-?early Campanian age is proposed. Lamniform sharks are the best represented group in terms of taxic diversity and relative abundance, probably reflecting the peak in diversity this group experienced following the Cenomanian radiation in the Late Cretaceous. The faunal assemblage of Akkermanovka exhibits significant taxonomic overlaps with assemblages reported from Asia and North America, but not from Southern Hemisphere continents, indicating east-west dispersal of several marine taxa during the Late Cretaceous.
Despite recent advances in noninvasive imaging, Plesiosauria remains one of the least explored clades of reptiles with respect to paleoneuroanatomy. Only partial endocasts, obtained from either latex casts or imprints left on the braincase, have been described. In this contribution, the digital endocasts of three plesiosaurian specimens were analyzed: two referred to the elasmosaurid Libonectes morgani and one to Polycotylidae indet., all from the Late Cretaceous (Turonian) of Goulmima (Morocco). They were computed tomography (CT)-scanned to provide new anatomical information on the plesiosaurian endocast, endosseous labyrinth, and cranial nerves. Results show that the three endocasts are very similar to each other. They appear anteroposteriorly elongated and horizontally oriented in lateral view, with long olfactory tracts, relatively small and incomplete olfactory bulbs, a reduced pineal organ, distinguishable optic lobes, and a possible large cerebellum constituting the main component in size of the endocast. The endocranial features reconstructed here are compared with those of other plesiosaurians, as well as other marine reptiles, notably to discuss their intraspecific and interspecific variability. This study provides pioneer data in order to estimate the impact of both phylogenetic and ecological constraints on the endocranial morphology of plesiosaurians and proposes a few preliminary paleobiological suggestions.
The holotype of Brancasaurus brancai is one of the most historically famous and anatomically complete Early Cretaceous plesiosaurian fossils. It derived from the Gerdemann & Co. brickworks clay pit near Gronau (Westfalen) in North Rhine-Westphalia, northwestern Germany. Stratigraphically this locality formed part of the classic European “Wealden facies,” but is now more formally attributed to the upper-most strata of the Bückeberg Group (upper Berriasian). Since its initial description in 1914, the type skeleton of B. brancai has suffered damage both during, and after WWII. Sadly, these mishaps have resulted in the loss of substantial information, in particular many structures of the cranium and limb girdles, which are today only evidenced from published text and/or illustrations. This non-confirmable data has, however, proven crucial for determining the relationships of B. brancai within Plesiosauria: either as an early long-necked elasmosaurid, or a member of the controversial Early Cretaceous leptocleidid radiation. To evaluate these competing hypotheses and compile an updated osteological compendium, we undertook a comprehensive examination of the holotype as it is now preserved, and also assessed other Bückeberg Group plesiosaurian fossils to establish a morphological hypodigm. Phylogenetic simulations using the most species-rich datasets of Early Cretaceous plesiosaurians incorporating revised scores for B. brancai, together with a second recently named Bückeberg Group plesiosaurian Gronausaurus wegneri (Hampe, 2013), demonstrated that referral of these taxa to Leptocleididae was not unanimous, and that the topological stability of this clade is tenuous. In addition, the trait combinations manifested by B. brancai and G. wegneri were virtually identical. We therefore conclude that these monotypic individuals are ontogenetic morphs and G. wegneri is a junior synonym of B. brancai. Finally, anomalies detected in the diagnostic features for other “Wealden” plesiosaurians have prompted reconsiderations of interspecies homology versus intraspecific variability. We therefore propose that the still unresolved taxonomy of B. brancai should emphasize only those character states evident in the examinable fossil material, and specifically accommodate for growth-related modifications delimited via osteologically mature referred specimens.
A fragmentary plesiosaur skull from lower Maastrichtian levels of the Conway Formation, New Zealand, is redescribed. Originally regarded as pertaining to two separate individuals, we argue that they represent a single individual belonging to a new aristonectine elasmosaurid, Alexandronectes zealandiensis gen. et sp. nov. This new taxon has common morphologies with other aristonectines such as expansion of the pterygoids extending posteriorly beyond the occipital condyle (as observed in Ar. quiriquinensis and probably in Kaiwhekea katiki) and the presence of an ‘A’-shaped squamosal arch in dorsal view. Otherwise, it is distinguished from these latter species by having different paraoccipital processes, a different mandibular glenoid, and an adult skull comparatively smaller than K. katiki and Aristonectes spp. The new taxon is a morphologically intermediate form between the dorsoventrally high skull of K. katiki and the mediolaterally expanded skulls of Aristonectes spp. The studied specimen is the second genus and species and the third report of an aristonectine recovered from lower Maastrichtian beds of New Zealand, emphasizing the diversity of this group in New Zealand and also indicating that aristonectines could include smaller species than those already known.http://zoobank.org/urn:lsid:zoobank.org:pub:5167B8FB-82F7-4F33-8663-EBF16692A9A0SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: Otero, R. A., J. P. O'Gorman, N. Hiller, F. R. O'Keefe, and R. E. Fordyce. 2016. Alexandronectes zealandiensis gen. et sp. nov., a new aristonectine plesiosaur from the lower Maastrichtian of New Zealand. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2015.1054494.
This chapter presents comparative cranial anatomy of two North American cretaceous Plesiosaurs. The skulls of Elasmosaurus morgani and Dolichorhynchops osborni are compared as representatives of the Cretaceous plesiosaur families Elasmosauridae and Polycotylidae, respectively. Cranial features and the atlas-axis complex appear to be more stable evolutionarily than postcranial features. Similarities indicate that the short-necked Cretaceous polycotylids are the sister group to long-necked elasmosaurids. This implies that the short-necked polycotylids of the Cretaceous are not descended from the short-necked pliosaurs of the Jurassic. The chapter further elaborated the significance of similarities between Libonectes and Dolichorhynchops. The short neck has appeared independently at least twice in the Plesiosauria, and the term "pliosaur" to refer any short-necked plesiosaur should be abandoned to avoid any phyletic implications. Differences between Elasmosaurus morgani and Elasmosaurus platyurus demonstrate that the two species belong to a different genera and a new name is proposed for E. morgani.
The site of Goulmima (south Morocco) is well known for its rich marine fauna of Turonian age (Late Cretaceous). It has yielded a large variety of invertebrates but also of vertebrate taxa, represented by actinopterygians and marine reptiles including Plesiosauria (Sauropterygia) and Mosasauroidea (Squamata). The Plesiosauria are known so far by two major clades of Plesiosauroidea: the Elasmosauridae (Libonectes atlasense Buchy, 2005) and the Polycotylidae (Thililua longicollis, Bardet, Suberbiola & Jalil, 2003a
; Manemergus angirostris Buchy, Metayer & Frey, 2005). Here we describe a new specimen of plesiosaur found in the same outcrop, differing from those previously cited and belonging to the other large plesiosaur clade, the Pliosauroidea. Comparison of this specimen with other Plesiosauria shows that it belongs to Brachauchenius lucasi Williston (1903), a species previously known only from the Cenomanian–Turonian stages of the Western Interior Seaway of North America and in the upper Barremian succession of northern South America (Colombia). The description of this species on a contemporaneous site of North Africa significantly expands its palaeobiogeographic distribution. This discovery confirms the affinities between marine faunas of the Western Interior Seaway and those of North Africa at this time, and also permits a better understanding of the palaeobiology of the Goulmima outcrop. A discussion about the systematical status of Polyptychodon Owen, 1841 is also provided.
In recent years, large numbers of Early Turonian ammonites from Morocco have found their way onto the open market. They come from the Cretaceous escarpment to the north of Goulmima, in the province of El Rachidia, southern Morocco. A section measured northeast of the village of Asfla sets the ammonites in stratigraphic context. The fauna belongs to the widely recognised upper lower Turonian Mammites nodosoides Zone, and comprises Romaniceras (Yubariceras) reymenti (COLLIGNON, 1967), Mammites nodosoides (SCHLÜTER, 1871), Nannovascoceras intermedium RENZ & ALVAREZ, 1979, Fagesia peroni PERVINQUIÈRE, 1907, Neoptychites cephalotus (COURTILLER, 1860), Neoptychites aff. hottingeri COLLIGNON, 1967, Choffaticeras (Choffaticeras) segne (SOLGER, 1903) and Wrightoceras munieri (PERVINQUIÈRE, 1907).
The osteology of the Cretaceous teleost Goulmimichthys arambourgi is described, and its phylogenetic relationships are discussed. According to a cladistic analysis, this species is included in the family Pachyrhizodontidae and in the sub-order Pachyrhizodontoidei. The robustness of the cladistic analysis is tested by experimental analysis of the data set. Diagnostic characters are proposed for the Protobramoidei nov., the Pachyrhizodontoidei, the Notelopidae and the Pachyrhizodontidae. Pachyrhizodontids were marine ichthyvorous fishes, which probably became extinct at the Cretaceous-Tertiary boundary.
Among the most enigmatic and controversial plesiosaurian clades is the Early Cretaceous Leptocleididae, a small group of (mostly) short-necked taxa with ‘intermediate' or ‘pliosauromorph' body proportions. Leptocleidids have often been interpreted as basal members of Pliosauroidea, and their presence in marginal marine and even freshwater facies has led to suggestions that they might represent late-surviving relicts, perhaps related to the Lower Jurassic rhomaleosaurids. We describe a new leptocleidid, Vectocleidus pastorum gen. et sp. nov., from the late Barremian part of the Cowleaze Chine Member (Vectis Formation), Isle of Wight, UK, and undertake a detailed reassessment of leptocleidid anatomy and relationships. New data on the long-necked Brancasaurus gives extra support to a monophyletic Leptocleididae with taxa of ‘intermediate' body plan and robust skulls, Leptocleidus superstes, Leptocleidus capensis, Nichollssaura and Vectocleidus. Thus, leptocleidids adopted a range of body plans on the pliosauromorph–plesiosauromorph spectrum. Support for a placement of Leptocleididae within Pliosauroidea is weak, and most proposed synapomorphies fail the test of similarity. However, numerous synapomorphies, including many new observations, support a derived position within Plesiosauroidea. Thus, the ‘intermediate' body plan of many leptocleidids is not plesiomorphic, and plesiosaurian body plan evolution was complex and highly plastic. We also summarize the anatomy of ‘Cimoliasaurus' valdensis, a short-necked Early Cretaceous taxon. ‘C.' valdensis is a valid taxon for which we erect the new monotypic genus Hastanectes. Hastanectes shows evidence of possible pliosaurid affinities. Thus, multiple plesiosaurian clades may have invaded margin and freshwater environments.http://zoobank.org/urn:lsid:zoobank.org:pub:8A0A8BD0-F6BB-4F74-BB18-79CBBA2F105C
The Eulert pliosaurid remains (FHSM VP-321) housed at the Sternberg Museum of Natural History (Kansas, U.S.A.) include one of the world's best examples of a Cretaceous pliosaurid plesiosaur skull. The specimen's original assignment to Brachauchenius lucasi was based solely upon the skull (dorsal surface) and left lower jaw (lateral view) because the specimen was embedded in a plaster mount. The history of B. lucasi is similarly problematic, because the type and a referred skull were formerly visible only in ventral and dorsal views, respectively. Further preparation and comparison of these specimens reveal new data about the arrangement of cranial elements. The Eulert pliosaurid bears several distinct autapomorphies as compared with B. lucasi, including cranial proportions (pretemporal length of palate longer, shorter temporal fenestrae), configuration of skull roof elements (frontals participate in premaxilla-parietal suture, suture occurs further forward), and configuration of the palate (posterior vomers not masked by medial alar extensions of the palatines, caudal vomerian fenestrae positioned further posterior, long slit-like anterior pteryoid vacuity present). Furthermore, FHSM VP-321 possesses double-headed cervical ribs, a feature previously unknown in Cretaceous pliosaurids. This combination of characters merits separation of the Eulert pliosaurid and a referred specimen to a new taxon, Megacephalosaurus eulerti. The type and paratype skulls of M. eulerti are 1.5 m and 1.75 m in length, respectively, and thus 50% and 75% larger than the known 1-m-long skulls of B. lucasi, suggesting that M. eulerti may attain larger size than B. lucasi.
The type specimen of Elasmosaurus platyurus Cope, 1868 from the Upper Cretaceous (lower Campanian) of Kansas, U.S.A. is redescribed. It consists of part of the skull (e. g., both premaxillae, parts of the maxillae, the occipital condyle and parts of the dentaries), the almost complete vertebral column, including the atlas-axis complex, as well as the pectoral and pelvic girdles (although the latter are now lost). The genus Elasmosaurus can be defined by two unambiguous autapomorphies, the presence of six premaxillary teeth and the high number of 71 cervical vertebrae. It also exhibits a number of advanced features, which are discussed and compared with other elasmosaurs.
Aspects of the cranial osteology of the early elasmosaurid Muraenosaurus are discussed. The quadrate complex is similar to other early elasmosaurids; the vomer-pterygoid contact is at variance with existing descriptions. The brain case and basis cranii show considerable ontogenetic variation. The position of the fenestra vestibularis, which is large and well developed, as well as the canalis fallopii are established and a new interpretation of the middle ear is provided. Inner and middle ear as well as the entire brain case of plesiosaurs, as exemplified by Muraenosaurus, are close to the ground plan of the Diapsida. The neurocranium of Muraenosaurus is compared to that of the Triassic sauropterygians Nothosaurus and Simosaurus. It is concluded that it differs strongly, being less advanced in many respects. This indicates that nothosauroids and plesiosauroids are sister groups.
ABSTRACT—This paper describes a new species of elasmosaurid plesiosaur,Aristonectes quiriquinensis, sp. nov., based on a partial skeleton recovered from upper Maastrichtian beds of the Quiriquina Formation of central Chile. The material described here consists of two skeletons, one collected near the village of Cocholgue, and a second juvenile specimen from Quiriquina Island. Prior to these finds,Aristonecteswas viewed as a monospecific genus, including only the enigmaticAristonectes parvidens, the holotype of which consists of an incomplete skull and incomplete postcranium. Other material referred to the genus
includes an incomplete juvenile skull and other postcranial material from the upper Maastrichtian of Antarctica, as well as a partial skull from the Quiriquina Formation of central Chile. The relationships ofAristonecteshave been controversial, with competing theories assigning the genus to Cryptoclididae, Elasmosauridae, and Aristonectidae; however, there is a developing consensus thatAristonectesis a derived elasmosaurid, and this paper gives strong evidence for this view. Comparison of the specimen here studied with the holotype ofA. parvidensdemonstrates thatA. quiriquinensisis a distinct species. The completeness of the adult skeleton allows the first confident size estimates for adultAristonectes. It is a large plesiosaurian with a relatively large skull with numerous homodont teeth, a moderately long and laterally compressed neck, and relatively narrow trunk, with slender and elongate forelimbs. The two specimens are restricted to the upper Maastrichtian of central Chile, posing questions concerning the austral circumpolar distribution of different elasmosaurids towards the end of the Cretaceous.
The braincase of a polycotylid plesiosaur referable to Dolichorhynchops from the Niobrara Formation (Santonian to the earliest Campanian) in Manitoba, Canada, is described. The well-preserved material without matrix permits observation of various anatomical features of the polycotylid braincase with unprecedented clarity. A virtual reconstruction of the braincase was created by using a three-dimensional scanning technique that produces accurate reconstruction of missing or damaged elements and demonstrates the three-dimensional relationships among the elements. Comparison with other plesiosaurian braincases revealed previously unrecognized characters and character states. The I-beam-shaped parasphenoid, the relatively short pituitary fossa, and the anterior process of the prootic are possible synapomorphies of the Polycotylidae or of its subclades. It could be a challenge to confirm the presence of the supraoccipital process and its median ridge, as well as the presence of the fenestra ovalis, in polycotylid skulls because of the location and orientation of these structures. Variable morphology of basioccipital-basisphenoid contact and the paroccipital process in Dolichorhynchops and related taxa require further investigation. The I-beam of the parasphenoid and the wide contact surfaces of the basioccipital and neighboring elements provide more resistance to flexion of the braincase. Distribution of the extensive pterygoid-basicranium contact, the shape of foramen magnum, anterior process of the prootic, and the short pituitary fossa do not confirm the current phylogenetic hypotheses. The location and orientation of the fenestra ovalis suggest the lack of a tympanic ear in this plesiosaur.
Turonian deposits of the Goulmima area, Er-Rachidia Province in southern Morocco, have yielded a diverse marine vertebrate fauna, including chondrichthyans, bony fishes, and large marine reptiles such as plesiosaurians, mosasauroids, and turtles. These fossils are included in ovoid calcareous nodules that are difficult to prepare. Moreover, bones may be partially or totally dissolved, making their study difficult. Using computed tomography, we have reconstructed the entire skull anatomy of SMNS 81783, one of the rare plesiosaurian specimens found in this locality and more generally in Africa. The digital three-dimensional reconstruction of the skull and the mandible offers for the first time the possibility to describe this specimen exhaustively. The new anatomical characters recorded confirm that SMNS 81783 belongs to Elasmosauridae on the basis of (1) slender and triangular skull; (2) beak index equal to 42%; (3) temporal fossa estimated to occupy about 40% of the skull length; (4) long process of the premaxillae extending posteriorly to meet the parietal above the orbit and separating the frontals; and (5) margin of the temporal fenestra lacking obvious contribution from the frontal. A preliminary phylogenetic analysis confirms its elasmosaurid affinity. The relationships between SMNS 81783, Libonectes atlasense, and Libonectes morgani, as well as the presence of stapes and pineal foramen, are discussed.
SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVP
Citation for this article: Allemand, R., N. Bardet, A. Houssaye, and P. Vincent. 2017. Virtual reexamination of a plesiosaurian specimen (Reptilia, Plesiosauria) from the Late Cretaceous (Turonian) of Goulmima, Morocco, using computed tomography. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2017.1325894.
Zverkov, N.G., Averianov, A.O. & Popov E.V., April 2017. Basicranium of an elasmosaurid plesiosaur from the Campanian of European Russia. Alcheringa March. ISSN 0311-5518
The braincase of elasmosaurid plesiosaurs is poorly known. Here, we describe the exceptionally well-preserved elasmosaurid basicranium from the Rybushka Formation (lower Campanian) of Saratov Province, Russia. The material provides new anatomical information and peculiar features: single anterior foramen for the cerebral carotid arteries, anteroposteriorly elongated sella turcica and deep canal on the basioccipital process. This allow us to reconstruct a carotid circulation in plesiosaurs and propose new basicranial features (anteroposteriorly elongated sella turcica and single anterior foramen for the cerebral carotids), which could be potentially synapomorphic for a clade within the Elasmosauridae.
Nikolay G. Zverkov* [zverkovnik@mail.ru], Department of Palaeontology, Geological Faculty, Lomonosov Moscow State University, 1 Leninskie Gory, 119991 Moscow; Laboratory of Phanerozoic Stratigraphy, Department of Stratigraphy, Geological Institute of the Russian Academy of Sciences, Pyzhevsky lane 7, 119017 Moscow, Russia; Alexander O. Averianov [dzharakuduk@mail.ru], Zoological Institute of the Russian Academy of Sciences, Universitetskaya Emb. 1, Saint Petersburg 199034; Department of Sedimentary Geology, Geological Faculty, Saint Petersburg State University, 16 liniya VO 29, 199178 Saint Petersburg, Russia; Evgeny V. Popov [elasmodus74@gmail.com], Department of Historical Geology and Paleontology, Geological Faculty, Saratov State University, 83 Astrakhanskaya Str., 410012 Saratov; Institute of Geology and Petroleum Technology, Kazan Federal University, Kremlevskaya Str. 4/5, 420008 Kazan, Russia.
The holotype of Libonectes atlasense is an almost complete skeleton from Upper Cretaceous (mid-Turonian)
rocks of the Goulmima area in eastern Morocco. Initial assessment of this specimen in 2005
proposed generic referral based on stratigraphical contemporaneity with Libonectes morgani from the
CenomanianeTuronian of Texas, U.S.A. Nevertheless, relative differences in the profile of the
premaxillary-maxillary tooth row, position of the external bony nasal opening, number of teeth and
rostrad inclination of the mandibular symphysis, proportions of the axial neural arch, and number of
cervical and pectoral vertebrae were used to distinguish between these species. As part of an on-going
comparative appraisal of elasmosaurid plesiosaurian osteo-anatomy, we re-examined the type and
formally referred material of both L. atlasense and L. morgani in order to establish species validity, as well
as compile a comparative atlas for use in future works. Our inspections revealed that these reportedly
distinct species-level fossils are in fact virtually indistinguishable in gross morphology. Indeed, the only
substantial difference occurs in relative prominence of the midline keel along the mandibular symphysis,
which might be explained by intraspecific variation. Furthermore, our observations permit an amendment
to the published generic diagnosis of Libonectes with the confirmation of important states such as
the likely presence of a pectoral bar, distocaudad expansion of the humerus, and an epipodial foramen. In
addition, novel features include a prominent ‘prong-like’ ventral midline process on the coracoids, and
the development of a median pelvic bar that encloses a central fenestration. The composite remains of
L. morgani thus constitute one of the most complete elasmosaurid skeletal hypodigms documented
worldwide, and evidence a trans-Atlantic distribution for this apparently dispersive species during the
earlyeLate Cretaceous.
The systematics of elasmosaurids are not well resolved partially because of the scarcity of well-preserved skull material. Among Weddellian elasmosaurids, one exception to this is the holotype of Tuarangisaurus keyesi from upper Campanian–lower Maastrichtian levels of the Maungataniwha Sandstone Member of the Tahora Formation, Mangahouanga Stream, inland Hawke's Bay, New Zealand. The material preserves an almost complete cranium and mandible. This material is re-described here, based on new observations and digital reconstruction of the internal anatomy. The result adds one new autapomorphy to the diagnosis of the taxon: ectopterygoid with large boss on the ventral surface and a posteriorly directed process. AdNew features are recorded: presence of stapes; pterygoid overlapping the vomer, medial sulcus on the dorsal surface of the vomer, parasphenoid–basisphenoid complex covering the ventral surface of the body of the basioccipital. The presence of stapes in Tuarangisaurus keyesi is surprising as they were previously considered absent among elasmosaurids. Phylogenetic analysis indicates a clear elasmosaurid affinity, although there is low resolution within the Elasmosauridae. The previously proposed close relationship with the early Aptian Callawayasaurus colombiensis is rejected.
A partial exoccipital–opisthotic from the uppermost lower Campanian (Upper Cretaceous) of the Åsen locality, Kristianstad Basin, southernmost Sweden, is described and illustrated. The fossil represents the first braincase element of a plesiosaur found in Sweden. It includes the chamber for the ampulla and utriculus, openings for the caudal vertical and horizontal semicircular canals, and four foramina for cranial nerves. The incomplete braincase can be referred to an elasmosaurid plesiosaur, and closely resembles the exoccipital–opisthotic of Libonectes morgani and a referred specimen of Aristonectes parvidens. Although we discuss putative postcranial material of the elasmosaurid subfamily Aristonectinae in the uppermost lower Campanian of southernmost Sweden, the exoccipital–opisthotic from Åsen most likely belongs to a juvenile individual of a non-aristonectine elasmosaur.
A new polycotylid plesiosaur from the early Turonian (Upper Cretaceous) of the region of Goulmima, Morocco, is described. The holotype of Manemergus anguirostris n. gen. et sp. comprises the subcomplete axial skeleton and partial appendicular skeleton of an articulated juvenile individual. Owing to the young age of the specimen, the nature of anatomical variation during ontogeny in plesiosaurs is discussed. The new taxon is characterised by its skull architecture combining a narrow, relatively short rostrum and a box-like post-orbital segment, and slender, smooth teeth. The state of preservation of the specimen hints at a relative in vivo stiffness of the neck due to strong ligamentous intervertebral connections.
Leptocleidus Andrews, 1922 is a poorly known plesiosaur genus from Lower Cretaceous successions of the UK, South Africa, and Australia. Historically, there has been little consensus regarding its phylogenetic position within Plesiosauria, largely because of its seemingly aberrant combination of a relatively small skull and short neck. As a result, a diverse array of potential sister groups have been posited for Leptocleidus, including long-necked Cretaceous elasmosaurids, Early Jurassic "rhomaleosaurs", and Middle to Late Jurassic pliosaurids. A cladistic analysis including Leptocleidus, and a new, apparently morphologically similar specimen from Alberta, TMP 94.122.01, was undertaken to assess their phylogenetic position within Plesiosauria. A character-taxon matrix was assembled afresh, consisting of 33 operational taxonomic units sampled broadly among plesiosaurs. 185 cranial and postcranial characters used in plesiosaur phylogenetics were critically reanalyzed, of which 152 were employed in the parsimony analysis. The results indicate a basal dichotomous split into the traditionally recognized pliosauroid and plesiosauroid clades. Nested within Pliosauroidea, a monophyletic Leptocleididae was recovered, consisting of L. superstes Andrews, 1922 and L. capensis (Andrews, 1911a). In contrast to earlier suggestions, Leptocleidus neither clusters with Rhomaleosaurus, which was found to be paraphyletic, nor with large-skulled pliosaurid taxa, such as Simolestes. Rather, a sister group relationship between Cretaceous Polycotylidae and Leptocleididae was recovered, which is here named Leptocleidoidea. Although TMP 94.122.01 is superficially similar to Leptocleidus, several discrete characters of the skull nest this new taxon within Polycotylidae. Compared to other phylogenetic hypotheses of plesiosaurs, these results are more congruent with respect to the stratigraphic distribution of leptocleidoids. A classification for Plesiosauria is presented.
A new locality yielding fossiliferous nodules is recorded in the Lower Turonian of Morocco near Goulmima (southern side of the Atlas). Most of the nodules contain fishes constituting one of the most important ichthyofaunas in the Turonian of North Africa. A new pachyrhizodontid is identified as Goulmimichthys arambourgi n. g., n. sp. This fish exhibits features of its own and features shared with Rhacolepis buccalis from the Albian of Brazil and/or with the genus Pachyrhizodus, which first appears in the Albian of Europe and is known world-wide in the Upper Cretaceous. -English summary
A new plesiosaur taxon, Nichollsia borealis, gen. et sp. nov., from the Wabiskaw Member of the Clearwater Formation (Lower Cretaceous, Albian) of northeastern Alberta, Canada, is described. The exceptionally well-preserved, almost complete, fully articulated specimen represents the oldest known, and one of the most complete, Cretaceous plesiosaurs from North America. High resolution computed tomographic data of the skull provide detailed information regarding cranial structure. Nichollsia is compared to other Cretaceous genera, including Leptocleidus, with which it shares similar skeletal proportions, size, and the presence of a prominent dorsomedian ridge on the premaxillae. Nichollsia, however, possesses numerous autapomorphies, including the possession of a gracile, narrowly triangular skull lacking a rostral constriction, a vertically oriented Suspensorium, a squamosal vertex that lacks a prominent crest, the presence of longitudinal grooves on the lateral surface of the dentary, a relatively homodont dentition lacking caniniforms, and other unique features of the axial and appendicular skeleton. Nichollsia inhabited the Boreal Sea, the first major marine incursion into the northern part of the Western Interior Basin in the Early Cretaceous prior to the establishment of the Western Interior Seaway.
ABSTRACT—A new elasmosaurid, Vegasaurus molyi, gen. et sp. nov., from Vega Island, James Ross Archipelago, Antarctica, is described. The holotype and only specimen of this species (MLP 93-I-5-1) was collected from the lower Maastrichtian Cape Lamb Member of the Snow Hill Island Formation. Vegasaurus molyi is the only Antarctic elasmosaurid and one of only a few Late Cretaceous elasmosaurids from the Southern Hemisphere whose postcranial anatomy is well known. Vegasaurus molyi is distinguished from other elasmosaurids by the following combination of characters: cervical region with 54 vertebrae with elongated centra, dumbbell-shaped articular faces and lateral ridge present in the anterior and middle parts of the neck but absent in the posterior-most cervical vertebrae; scapula with ventral ramus bearing a strong
ridge in the anteromedial corner of its dorsal surface; ilium shaft with expanded distal end, divided into two parts forming an angle of 140� opening anteriorly; and humerus with anterior knee and prominent posterior projection with accessory posterior articular facet. Preliminary phylogenetic analysis places V. molyi within a clade that includes the Late Cretaceous Weddellian aristonectine elasmosaurids, Aristonectes and Kaiwhekea. This indicates a close relationship between Aristonectinae and non-Aristonectinae Late Cretaceous Weddellian elasmosaurids and suggests a Weddellian origin for the Aristonectinae.
Elasmosauridae constitutes one of the most immediately recognizable plesiosaurian radiations. Their distinctive body plan represents the popular model for Plesiosauria, and is typified by an osteological morphology especially adapted for hyper-elongation of the neck. Nevertheless, many archetypal elasmosaurids are known only from incomplete and/or inadequately documented material, a problem that has contributed to their uncertain intra-clade relationships. A prime example of this is
Libonectes morgani
from the Upper Cretaceous of Texas, USA, which is frequently presented as an elasmosaurid structural proxy because of its three-dimensionally preserved holotype skull. Perplexingly though, both the taxonomic diagnosis and phylogenetic placement of
L. morgani
rely primarily upon the cervical vertebrae, together with the pectoral girdle and forelimb, yet most of these elements are now lost and figured only as line drawings. We therefore reviewed the remnant postcranial skeleton of
L. morgani
first-hand with the objective of clarifying its defining character states. Our observations showed that the existing diagnosis of
L. morgani
is indeed inadequate. Moreover, the only identifiable autapomorphies occurred within the axial skeleton. This concurred with an examination of character scores used in published plesiosaurian phylogenies, and highlights the persistent significance of postcranial elements for discriminating elasmosaurid taxa.
The Lower Cretaceous (upper Berriasian to lowermost Aptian) nonmarine Wealden succession of southern England has been a prolific source of vertebrate fossils for over 180 years. The sequence is most famous for terrestrial reptiles, particularly dinosaurs; however, significant aquatic tetrapod discoveries including rare nonmarine plesiosaurs have also been reported. The record of Wealden plesiosaurs currently incorporates a single valid taxon, Leptocleidus superstes Andrews, 1922a, based on a partial skeleton and skull from the Barremian Upper Weald Clay Formation of Berwick, Sussex. Traditional classifications place this plesiomorphic pliosauroid with basal Jurassic rhomaleosaurids; however, the genus Leptocleidus has since become a ‘waste basket’ for various Cretaceous rhomaleosaurid-like plesiosaurs from around the globe. In an attempt to clarify this situation, the type specimen of L. superstes was reexamined and redescribed. Previously unrecorded anatomical features were identified including an elongate, gracile paraoccipital process on the exoccipital-opisthotic, and tooth ornament comprising widely spaced, coarse striations that are restricted to the lingual surface of the crown (mesiodistal ‘carinae’ are absent). Other indeterminate pliosauroid remains (recovered along with coeval elasmosaurids) from the upper Berriasian–Valanginian Hastings Beds Group also exhibit potentially diagnostic traits: an atlas centrum with no anterolateral exposure and with ventral margin formed by the intercentrum; a single-headed rib articulation on the atlas centrum extending onto the axis centrum; and epipodials that are longer than broad. The placement of L. superstes is controversial in recent phylogenies. To test the competing hypotheses, L. superstes together with all closely related species were rescored into the most comprehensive published phylogenetic data sets of Plesiosauria and Pliosauroidea. Separate maximum parsimony and Bayesian analyses of each matrix unanimously supported a relationship between L. superstes and pliosauroids but could not confirm placement within either Rhomaleosauridae sensu stricto, or a discrete ‘leptocleidoid’ clade. Examination of character states advocating affinities amongst Leptocleidus spp. suggests homoplasy rather than clear homology between what are potentially palaeobiogeographically disparate genus-level taxa. © 2011 The Linnean Society of London, Zoological Journal of the Linnean Society, 2011, 161, 663–691.
This chapter discusses morphological and taxonomic clarification of the genus Plesiosaurus. Detailed examination of the broad range of English Liassic plesiosaur species indicates that only Plesiosaurus dolichodeirus and its junior synonyms can be assigned to Plesiosaurus. Many named Plesiosaurus species are based on inadequate material and considered nomina dubia. While others even those contemporaneous with P. dolichodeirus, are certain or probable representatives of distinct genera exhibiting significant cranial autapomorphies. The chapter elaborates that only the German Lower Jurassic, notably the Holzmaden Lagerstatte, and the French upper Toarcian currently contain taxa that are potentially valid specific variants of Plesiosaurus. P. dolichodeirus has relatively short antorbital and temporal regions, subcircular temporal fenestrae, a broad but pointed rostrum, and a large pineal opening. P. dolichodeirus also has a nonspatulate mandibular symphysis, approximately 40 cervical vertebrae with distinctly doubled rib facets, slightly rugose articular edges to virtually all vertebrae, a sharp posterolateral expansion to the coracoid, slightly longer forelimbs than hindlimbs, a curved humerus with a shallow interepipodial groove on its ventral surface, but no sharp anterodistal comer, and other identifying features.
A new elasmosaurid plesiosaur, Albertonectes vanderveldei, gen. et sp. nov., is described on the basis of an almost complete postcranial skeleton from the upper Campanian, Bearpaw Formation in Alberta, Canada. The new taxon is distinguished by a unique set of characters—76 cervicals, lateral longitudinal ridge on posterior-most cervicals, relatively wide clavicular arch, tapered ventral projection at the median symphysis of coracoids, pointed anterolateral projection of pubis, fused posterior-most caudal vertebrae, and a relatively slender humerus. Ninety-seven chert gastroliths were also recovered with the specimen, and their mean diameters range from
The plesiosaur specimen NHMUK 36184 from the Lower Jurassic of Whitby, Yorkshire and kept in the Natural History Museum of London, comprises an almost entire skeleton with nearly complete skull. It was described as one of two syntypes of Plesiosaurus homalospondylus by Owen, and selected as the lectotype by Lydekker. Extensive preparation of the skull has revealed it as one of the most complete and best-preserved Jurassic plesiosaurian skulls known, and its description adds much-needed data to our knowledge of the cranial osteology of the Plesiosauria. The three-dimensional preservation permits a relatively reliable reconstruction of its form. Microcleidus homalospondylus displays an interesting combination of cranial characters present in Jurassic plesiosauroids and Cretaceous Elasmosauridea. Its snout presents a very distinctive sculpture; the first pair of premaxillae teeth are extremely reduced; the frontal is partially overlain by the premaxillae, contacts the pineal foramen but does not contact the temporal fenestra; the jugal does not contact the orbit nor the temporal fenestra; the squamosal contacts the postorbital but not the maxilla and presents a bulb; the postfrontal contacts the posterolateral orbit margin; the anterior interpterygoid vacuity is absent; the pterygoids meet posterior to the posterior interpterygoid vacuities and are pierced by a foramen at this level; the quadrate ramus of the pterygoid presents a ventromedial flange; the parasphenoid is crested; the epipterygoid contacts the parietal; the paroccipital process is spatulate distally; the prootic presents an anteroventral process; the mandibular symphysis is keeled and bears four pairs of teeth. Microcleidus appears very similar to Hydrorion and Occitanosaurus, and the three taxa share a great number of plesiomorphic characters with basal plesiosaurians and pliosauroids.
An exceptionally complete skull, mandible and other bones of Pliosaurus brachyspondylus were collected from the Kimmeridge Clay of Westbury, Wiltshire, in 1980. The recovery and preparation of this large specimen required special techniques. The specimen is apparently part of a more complete skeleton, mostly destroyed before discovery. The decayed carcass was apparently disrupted so that the skull finally lay upside down over many of the teeth, which had fallen out, while the mandible lay several metres away. The reasons for this are unclear. The skull does not differ markedly from the usual pliosauroid pattern, being long and low, with a wide gape, narrow snout, and high temporal region. There are no nasals. The mandible cannot be satisfactorily reconstructed due to crushing but does not appear to deviate from the usual pliosauroid pattern. The dentition is robust and caniniform anteriorly, presumably to penetrate, hold and kill large prey. The posterior teeth are hook-shaped posteriorly to act as ratchets, helping to move large prey items back into the gullet. The jaw musculature is reconstructed as a dual-function system, the pterygoideus musculature being specialized to close the open jaws rapidly against inertia and drag, and the main adductor mass being specialized to clamp the jaws tightly onto prey. The cranial skeleton is well adapted to resist bending stresses induced when the animal bit onto prey. However, there is no evidence for any adaptation to torsional resistance, such as a pterygoid flange-mandible contact, as would be useful in twist-feeding to dismember large prey. Pliosaurus, at about 10 m overall length, may have been large enough to swallow most potential prey without being particularly specialized to dismember it. Its wide gape would help it swallow large prey. However, the comparatively narrow anterior snout, and evidence from gut contents in other specimens, suggest that it was an opportunistic feeder on a wide variety of prey of different sizes, including cephalopods and presumably fish and other reptiles. Large orbits and the lack of acoustically isolated ears indicate that it was primarily a visual hunter. The nares seem too small to be used in respiration, and may instead have been used in underwater olfaction.
While on a visit to Charles E. Leeds, Esq., M.A., of Exeter College, Oxford, a gentleman whose specimens have more than once enriched the writings of Professor Phillips, I was shown a Saurian in such perfect preservation as previously, so far as I am aware, had rarely been seen except from the Lias. It was gathered from the Lower Oxford Clay (a stratum abounding in Plesiosaurians in the middle of England) in Huntingdonshire, in fragments almost innumerable, which have been adjusted and reunited with remarkable skill and zeal by the labours of Mr. Charles Leeds and his brother Mr. Alfred Leeds, so that now the animal displays:—the front and hinder parts of the skull; the lower jaw, somewhat over a foot long; a vertebral column of 79 vertebræ, from which, however, nearly all the tail is missing—the vertebræ preserved being 44 cervical, 3 pectoral, 20 dorsal, 4 pelvic, and 8 caudal; numerous ribs; the coracoids and scapulæ; the pubes, ischia, and iliac bones, together with both fore and hind limbs.
Extract
Plates XLIII., XLIV., XLV.
Lord cole having done me the honour to transmit to me for description, his unique specimen of the Plesiosaurus macrocephalus, I have endeavoured to devote to it an examination equivalent in care and detail to the admirable completeness of many of its parts, and have reason to hope that it will throw additional light on the Plesiosaurian modifications of the vertebrate skeleton, as well as on some interesting points in general osteology. The study of the spinal column has induced me to reconsider the views generally adopted as to the composition of a vertebra; and I have found it convenient, if not absolutely requisite, to give new names, applicable both in the abstract and concrete senses, to some of the component vertebral elements. The chief specific characters are also premised of another Plesiosaur, which, from the completeness of its skeletons in our national and other collections, it seemed most advantageous to adopt as a term of comparison with the present specimen.
The species to which I refer, is that which is described and figured in Mr. Hawkins’s memoir on Ichthyosauri and Plesiosauri *, under the name of Triatarsostinus; but as this designation relates to an imperfect state of the tarsus in the right foot, (for a fourth bone is present in the left tarsus of the same specimen, and a second specimen of the same species in Mr. Hawkins’s collection exhibits five tarsal bones on each side,) I propose to refer to it under the name
Features observed in the skull, girdles and limbs of the Plesiosaur recently discovered at Tournemire (Aveyron) allow its assignment to the genus PlesiosaurusConybeare, 1821 with the systematic content of Persson. The specimen exhibits a novel association of anatomical features and is so regarded as the type of a new species: Plesiosaurus tournemirensis nov. sp. Discovered in Upper Toarcian Beds, the species could be a descendant of P. brachypterygiusV. Huene from the Middle Toarcian of Holzmaden (Western Germany).
Tethysaurus nopcsai gen. et sp. nov. is described on the basis of both cranial and postcranial material from the Late Cretaceous (Early Turonian) of the Goulmima region, southern Morocco. This new mosasauroid is mainly characterized by a parietal table ending posteriorly in two pointed pegs; jugal with a large ascending ramus; splenial with a large and notched dorsomedial process; surangular exposed medially ventral to the coronoid; large paracotylar and parazygosphenal foramina on vertebrae. A phylogenetic analysis shows that Tethysaurus is the sister-group of Mosasauridae. It fills the gap between the aigialosaurids (mainly Cenomanian) and the mosasaurids (known from the Middle-Late Turonian to the Latest Maastrichtian). To cite this article: N. Bardet et al., C. R. Palevol 2 (2003).
La localité à nodules fossilifères du Turonien inférieur marin des environs de la ville de Goulmima (versant sud de l'Atlas marocain) fournit une riche faune d'Actinoptérygiens. Trois nouvelles espèces de téléostéens appartenant aux familles des Ichthyodectidae, des Araripichtbyidae et des Osmeroididae sont signalées. L'ichthyofaune de Goulmima présente un mélange de formes connues par ailleurs, soit en Amérique du Sud dans deux gisements d'âge Albien et Turonien, soit dans des gisements européens répartis entre l'Albien et le Campanien et de formes cosmopolites au Crétacé supérieur.