Cretaceous Turtles Research Articles

Chemical Composition of Thalassinoides Boxwork Across the Marine K–PG Boundary of Central New Jersey, U.S.A.

Thalassinoides isp. burrow networks filled with green to dark bluish-gray glauconite pellets occur in the Cretaceous to Paleogene Hornerstown Formation and in the uppermost 1–2 m of the underlying Upper Cretaceous Navesink and New Egypt Formations at many central New Jersey Cretaceous–Paleogene (K/Pg) boundary sections. Near the base of the Hornerstown Formation is a renowned bonebed, the Main Fossiliferous Layer (MFL), which contains isolated to articulated Cretaceous marine reptiles, turtles, birds, and crocodiles interpreted as a thanatocoenosis. We investigated the bulk chemical composition of the burrow fill and surrounding matrix in the largely unconsolidated sections of the K–Pg interval at two sites, Inversand and Walnridge (Meirs) Farm, New Jersey, using a Niton XL3t XRF analyzer to place them in proper stratigraphic context. Bulk matrix Zr and Ti concentrations decrease up section as a result of transgression, deepening, and increased distance from source areas. In contrast, an increase in K is attributed to greater amounts and maturity of the glauconite, due to decreasing sedimentation rates. Zr and Ti concentrations in burrow fills below the MFL are virtually the same as in overlying sediments above the MFL and much less than in the surrounding matrix. This suggests that burrows in the Cretaceous strata were passively filled with Paleogene sediments. K concentrations of burrow fills are generally intermediate between the high values encountered in the Paleogene matrix and the lower values of the Cretaceous matrix. Although this may have resulted from removal of glauconite during bioturbation and burrow filling, it is more likely that immature glauconite was sequestered in the burrow fills below the depth of glauconitization before it could attain full maturity. Therefore, burrows originating above the formational contact at or above the MFL penetrate as much as two meters into underlying Cretaceous sediments, and are passively filled with Paleogene sediment. Burrows originating above the MFL may translocate diagnostic Danian microfossils, shocked quartz, and Ir, effectively diffusing the K–Pg boundary. This research demonstrates that care must be taken in sampling pervasively bioturbated strata to avoid incorporating stratigraphically younger burrow-fill sediments.

The largest Cretaceous podocnemidoid turtle (Pleurodira) revealed by an isolated plate from the Bauru Basin, south-central Brazil

The Bauru Basin (south-central Brazil) fossils have largely contributed to understand the faunal composition of South American Cretaceous. Among those, several turtle specimens were retrieved from those deposits, all belonging to Podocnemidoidae, the single group known from the Basin. On the other hand, only incomplete shell elements indicate large turtles such as ‘Peirópolis A’. Another shell fragment, a large peripheral plate from the Marília Formation, is described here. Its lack of surface ornamentation, and deep sulci are generally typical for podocnemidoids. The plate exhibits a narrow knob slightly projected onto the pleuro-marginal sulcus, absent in any other Bauru Basin turtle. According to extant and fossil podocnemidoids measures, we estimated this individual reached 1 m of carapace length, exceeding in size all other taxa known from the Basin. This new report reveals a broader size variation among podocnemidoids from the Late Cretaceous of Bauru Basin and a morphological diversity previously unknown for the period, comparable to those of the Amazon Basin today, in which inhabits the largest extant podocnemidoid Podocnemis expansa. Furthermore, the occurrence of such large turtles implies the presence of perennial streams on the northeastern portion of the Bauru Basin during the Maastrichtian and a richer environment than previously thought.

A new turtle taxon (Podocnemidoidea, Bothremydidae) reveals the oldest known dispersal event of the crown Pleurodira from Gondwana to Laurasia

Pan-Pleurodira is one of the two clades of extant turtles (i.e. Testudines). Its crown group, Pleurodira, has a Gondwanan origin being known from the Barremian. Cretaceous turtle fauna of Gondwana was composed almost exclusively of pleurodires. Extant pleurodires live in relatively warm regions, with a geographical distribution restricted to tropical regions that were part of Gondwana. Although pleurodires were originally freshwater forms, some clades have adapted to a nearshore marine lifestyle, which contributed to their dispersal. However, few lineages of Pleurodira reached Laurasian regions and no representatives have so far been described from the pre-Santonian of Laurasia, where the continental and coastal Cretaceous faunas of turtles consist of clades exclusive to this region. A new turtle, Algorachelus peregrinus gen. et sp. nov., is described here from the southern Laurasian Cenomanian site of Algora in Spain. Numerous remains, including a skull and well-preserved postcranial specimens, are attributed to this species. The abundant shell elements, much more numerous than those known in most members of pleurodiran clade Bothremydidae, allow its variability to be studied. The new taxon represents the oldest evidence of the occurrence of Pleurodira in Laurasia, and is the oldest genus of the abundant and diverse Bothremydodda so far described. Factors such as the relatively high Cenomanian temperatures, the adaptation of this Gondwanan clade to coastal environments, and the geographical proximity between the two landmasses may have contributed to its dispersal. This finding shows that the first dispersals of Pleurodira from Gondwana to Laurasia occurred much earlier than previously thought.http://zoobank.org/urn:lsid:zoobank.org:pub:8FD358A5-53BD-4308-828A-AC6802184185

Turtles From an Arkadelphia Formation—Midway Group Lag Deposit (Maastrichtian—Paleocene), Hot Spring County, Arkansas, USA

The Arkadelphia Formation—Midway Group (Maastrichtian—Paleocene) contact near Malvern, Arkansas preserves a K-Pg boundary assemblage of turtle species consisting of skull, shell, and non-shell postcranial skeletal elements. The Malvern turtles are preserved within a coquina lag deposit that comprises the basalmost Midway Group and also contains an abundance of other reptiles, as well as chondrichthyans, osteichthyans, and invertebrates. This coquina lag deposit records a complex taphonomic history of exhumation and reburial of vertebrate skeletal elements along a dynamic ancestral shoreline in southwestern Arkansas during the late Cretaceous-early Paleocene. Based on stratigraphic occurrence, the Malvern turtle assemblage indicates that these marine reptiles were living at or near the time of the K-Pg mass extinction and represent some of the latest Cretaceous turtles yet recovered from the Gulf Coastal Plain of the United States.

Testudoid and crocodiloid eggshells from the Upper Cretaceous Deccan Intertrappean Beds of Central India

Chelonian and crocodilian eggs and eggshells are relatively rare in the fossil record as compared to those of dinosaurs and avians. In India, prior to the present report, turtle eggshells have been reported from the supposed Late Cretaceous infratrappean beds of Duddukuru, Andhra Pradesh. Likewise, crocodilian eggshells were described from the intertrappean beds of Bombay whose assignment to Maastrichtian age is not based on any age diagnostic fossils. Here we report the first definitive Late Cretaceous turtle and crocodilian eggshells from the intertrappean beds of Kisalpuri, Dindori District, Madhya Pradesh (Central India). The testudoid eggshells from Kisalpuri, though broadly comparable to those of Duddukuru, particularly in radial structure, differ from each other in finer details such as external surface ornamentation and the organization of crystallites in the radial section. The crocodiloid eggshells from Central India are distinct from known fossil eggshells in having non-interlocking wedge-like crystallites and ringed craters on the basal plate groups. Keeping in view the limited fossil specimens available for the present study, the testudoid and crocodiloid eggshells from the Late Cretaceous of Central India are referred to the oofamilies Testudoolithidae and Krokolithidae, respectively.

THE FOSSIL RECORD OF TURTLES IN COLOMBIA; A REVIEW OF THE DISCOVERIES, RESEARCH AND FUTURE CHALLENGES

This is a review article on the fossil record of turtles in Colombia that includes: the early Cretaceous turtles from Zapatoca and Villa de Leyva localities; the giant turtles from the Paleocene Cerrejon and Calenturitas Coal Mines; the early Miocene, earliest record of Chelus from Pubenza, Cundinamarca; the early to late Miocene large podocnemids, chelids and testudinids from Castilletes, Alta Guajira and La Venta; and the small late Pleistocene kinosternids from Pubenza, Cundinamarca. I also discuss here the current gaps in the fossil record of tropical South American turtles, as well as the ongoing research and future projects to be developed in order to understand better the evolutionary history of Colombian turtles.

Soft-shelled turtles (Trionychidae) from the Cenomanian of Uzbekistan

Localities from the Cenomanian of Uzbekistan are the oldest in Middle Asia and Kazakhstan to preserve two broadly sympatric species of trionychid turtle. Material described here comes from multiple Cenomanian formations from the Itemir locality, and from multiple localities in the Cenomanian Khodzhakul Formation. The first taxon from the locality, “Trionyx” cf. kyrgyzensis, has multiple morphological similarities with the older, Early Cretaceous “Trionyx” kyrgyzensis. In contrast, the second taxon, “Trionyx” dissolutus, has multiple similarities with “Trionyx” kansaiensis, one of two species of trionychid found in younger Late Cretaceous localities. “Trionyx” dissolutus bears some superficial resemblance to other trionychid taxa within the clade Plastomenidae because of its highly ossified plastron with a hyoplastral lappet and an epiplastral notch. However, Plastomenidae is diagnosed primarily through characters that are absent or cannot be observed in the available material of “T.” dissolutus, and other shared features are plesiomorphic. In addition, “T.” dissolutus shares other synapomorphies with Trionychinae. A heavily ossified plastron may be more homoplastric within Trionychidae than has been previously recognized. Finally, we provide an improved understanding of the subtle similarities and differences between several closely related Cretaceous turtle assemblages of Middle Asia and Kazakhstan.

Cretaceous soft-shelled turtles (Trionychidae) of Mongolia: new diversity, records and a revision

This paper is devoted to the description and revision of material of Cretaceous soft-shelled turtles (Trionychidae) of Mongolia. It includes the description of seven trionychid species, six of which are new, and two new genera: the cyclanorbine Nemegtemys conflata gen. et sp. nov. from the Nemegt Formation (Maastrichtian), and the trionychines Gobiapalone breviplastra gen. et sp. nov. from the Nemegt and Barungoyot (Campanian) formations, G. orlovi from the Baynshire Formation (Cenomanian–Santonian), ‘Trionyx’ baynshirensis sp. nov. from the Baynshire Formation, ‘T.’ gilbentuensis sp. nov. from the Nemegt Formation, ‘T.’ gobiensis sp. nov. from the Nemegt Formation, and ‘T.’ shiluutulensis sp. nov. from an unknown formation (Campanian). In addition, one shell from the ?Baynshire Formation of Khermin Tsav is assigned to Gobiapalone sp. The type material of Amyda menneri is considered to be Trionychidae indet. and Amyda menneri to be a nomen dubium. Finally, we revise other available materials of Cretaceous trionychids from 45 localities in Mongolia. Nemegtemys conflata, if correctly assigned, is the earliest known member of Cyclanorbinae. The two species of the new genus Gobiapalone are included in two phylogenetic analyses of Trionychidae. In both analyses Gobiapalone is monophyletic. In the first analysis, Gobiapalone is placed within Apalonina. In the second analysis, Gobiapalone is sister to Apalonina. Thus, the results of both analyses show that Apalonina, which is a rather advanced and well-supported trionychid clade, or its closest sister taxon (stem-Apalonina), were present in the Late Cretaceous of Asia. These results suggest that most other supra-generic clades of modern trionychids had been established in Asia by the Late Cretaceous. That suggestion is supported by the discovery of a cyclanorbine Nemegtemys conflata in the Late Cretaceous of Mongolia. Finally we summarize the latest data on temporal and geographical distributions of Cretaceous Trionychidae of Asia and North America.http://zoobank.org/urn:lsid:zoobank.org:pub:921DA1C5-C4B2-463D-A49D-608024C6036A

Derived appendicular morphology in Early Cretaceous aquatic turtles evidenced by the track record

A well-preserved isolated manus impression evidences the presence of derived aquatic adaptations in the forelimb morphology of Berriasian turtles. Size and the abundant co-occurring turtle fauna indicate that the track was left by a large-sized, bottom-walking basal pancryptodiran. The footprint shows an interesting mosaic of primitive and derived features. The basic turtle pattern is reflected by a short and broad autopodium but thin phalanges, claw reduction and extensive webbing enclosing the digits and lateral and medial margins of the distal metapodium are clearly specialized features related to the aquatic environment. Some characters including the proportional elongation of the first digit, which reached as far distally as the other digits and was probably highly mobile at the metacarpal-phalangeal joint, indicate an even higher degree of specialization. The specimen gives evidence on a hitherto unknown range of appendicular modification in Early Cretaceous turtles, and redundantly proves the aquatic habitat and locomotion of large-sized turtles from the Berriasian of northwestern Germany.

A new turtle from the Xiagou Formation (Early Cretaceous) of Changma Basin, Gansu Province, P. R. China

Changmachelys bohlini gen. et sp. nov., from the Lower Cretaceous Xiagou Formation, Changma Basin, north-western Gansu Province, adds to our understanding of the diversity and distribution of Early Cretaceous turtles in Asia. Changmachelys bohlini is similar to Early Cretaceous turtles from Asia included in “Macrobaenidae” in having a low domed carapace and a reduced, cruciform plastron with buttresses that do not extend onto the costals. With a carapace that exceeds 34 cm in length, it is one of the largest Early Cretaceous “macrobaenids”. Despite the addition of this new taxon and new characters to previous phylogenetic analyses, the relationships of “macrobaenid” turtles remain poorly resolved. In addition to adding to the diversity of “macrobaenid” turtles in the Early Cretaceous of Asia, Changmachelys bohlini is of interest because each of the four available specimens documents a distinct stage of ontogenetic development of the shell. In the carapace, the dermal portions of the costals are unossified in the most juvenile specimen but peripherals are present. In contrast with the late ossification of the dermal bone of the carapace, the plastron ossifies relatively early.

Soft-shelled turtles (Trionychidae) from the Bissekty Formation (Late Cretaceous: late Turonian) of Uzbekistan: Shell-based taxa

In this paper we describe previously unpublished trionychid turtle material, consisting of numerous shell fragments, from the Late Cretaceous (late Turonian) Bissekty Formation of the Dzharakuduk locality in Uzbekistan. This material is assigned to two shell-based taxa: Aspideretoides cf. riabinini and “Trionyx” cf. kansaiensis. The material which cannot be confidently attributed to these two taxa is identified as Trionychidae indet. In addition to these shell-based trionychid taxa, the Dzharakuduk turtle assemblage includes two skull-based taxa of trionychids (Khunnuchelys kizylkumensis and Trionychini indet.). The trionychids from the Bissekty Formation are most similar to trionychids from the younger (Santonian – early Campanian) Bostobe Formation of Kazakhstan, represented by three shell-based taxa (Aspideretoides riabinini, Paleotrionyx riabinini and “Trionyx”kansaiensis), and one skull-based taxon (Khunnuchelys sp.). We provide an improved understanding of the subtle similarities and differences between four closely related Cretaceous turtle assemblages of Middle Asia and Kazakhstan.

Larachelus morla, gen. et sp. nov., a new member of the little-known European Early Cretaceous record of stem cryptodiran turtles

ABSTRACT A relatively diverse record of European Early Cretaceous pan-cryptodiran turtles has been revealed from the analysis of new specimens and from a review of previously defined taxa. However, knowledge about many of these taxa remains relatively limited. We erect the new taxon, Larachelus morla, gen. et sp. nov., on the basis of a shell from the late Hauterivian–early Barremian of the Iberian Range (Spain). The comparative study of this taxon with the continental European Cretaceous pan-cryptodiran representatives and cladistic analyses reveal L. morla to be a member of the little-known European Early Cretaceous stem Cryptodira. Stem cryptodirans have been recognized from the Early Cretaceous of several continents. The study of L. morla not only confirms the presence of this group in the Early Cretaceous of Europe, it also provides new insights into the European evolution of Pan-Cryptodira. This finding reveals greater diversity in European Early Cretaceous continental pan-cryptodires, highlighting its Hauterivian–Aptian record. This diversity is particularly relevant in the Iberian Range, where several clades of turtles whose coexistence has not been recognized in the Lower Cretaceous of any other region are identified: paracryptodiran members, stem cryptodiran turtles, and representatives of several lineages of the crown group Cryptodira. This very high diversity of continental taxa shows a wide range of morphological diversity that could be related to adaptation to different ecological niches.

Galvechelone lopezmartinezae gen. et sp. nov., a new cryptodiran turtle in the Lower Cretaceous of Europe

Abstract: The Spanish town of Galve (Teruel) is notable because of the abundance of Upper Jurassic and, especially, Lower Cretaceous vertebrates recorded there. Although most groups have been studied in detail, information on turtles is very limited even though the material is relatively abundant. So far, no turtle taxa have been identified at the generic level. The only Lower Cretaceous articulated specimen from Galve is analysed here. It is identified as a representative of Cryptodira, Galvechelone lopezmartinezae gen. et sp. nov. Galvechelone lopezmartinezae is determined as a taxon belonging to the node that groups the turtles traditionally assigned to ‘Macrobaenidae’ and ‘Sinemydidae’, and other taxa such as the members of Panchelonioidea. This node, very abundant in the Lower Cretaceous of Asia, and with a broad subsequent distribution, has recently been recognized in the Lower Cretaceous of Europe. The diversity of basal members of Eucryptodira in the European Late Jurassic (represented by Thalassemydidae, Plesiochelyidae and Eurysternidae) was high. Owing to a relative scarcity of well‐preserved early Cretaceous turtles from Europe, the knowledge of this group of reptiles is limited. The study of the new turtle from Galve, together with the recently described Hoyasemys jimenezi, and the recently completed review of the enigmatic Chitracephalus dumonii demonstrate that members of the cryptodiran node grouping ‘Macrobaenidae’, ‘Sinemydidae’ and Panchelonioidea were also very diverse in this period.

A new species of Brodiechelys (Testudines, Pan-Cryptodira) from the Early Cretaceous of Spain: Systematic and palaeobiogeographic implications

Brodiechelys brodiei is an Early Cretaceous turtle from Great Britain, the only species of the genus. This taxon has been shown in recent phylogenies to be closely related to Xinjiangchelyidae and therefore could be the only representative of this group in Europe. Here, we present several specimens from the Early Cretaceous Maestrazgo Basin, in the Iberian Range of Spain attributed to the British genus, and to a new species, Brodiechelys royoi. This discovery shows that, as previously observed with terrestrial turtles, some freshwater turtle taxa had a wide European distribution during the Early Cretaceous, being present in both Britain and the Iberian Peninsula. This study sheds new light on the phylogenetic position of this enigmatic genus, supporting its attribution to Xinjiangchelyidae, a clade whose presence has been previously confirmed exclusively from the Middle Jurassic to Early Cretaceous of Asia. We propose that another recently identified taxon from the Iberian Peninsula (i.e., Larachelus morl...

First Cretaceous turtle from Antarctica

MARCELO DE LA FUENTE,12 FERNANDO E. NOVAS,* 13 MARCELO P. ISASI,1 3 JUAN M. LIRIO,4 and HECTOR J. NUNEZ4; Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET); 2Museo Municipal de Historia Natural de San Rafael, Parque Mariano Moreno S/N° San Rafael (5600), Mendoza, Argentina; 3Museo Argentino de Ciencias Naturales Bernardino Rivadavia, Av. Angel Gallardo 470, Buenos Aires (1405), Argentina, fernovas@yahoo.com. ar; 4Direccion Nacional del Antartico-Instituto Antartico Argentino, Cerrito 1248, Buenos Aires (1010), Argentina

First evidence of a Late Cretaceous sea turtle from Australia

The isolated scapula of a chelonioid sea turtle is described from the Upper Cretaceous (upper Maastrichtian) Miria Formation of the Giralia Ranges in Western Australia. Character states including the wide angle of divergence between the scapular processes (possibly reaching 140°), projection of the glenoid on a constricted scapular neck, and highly vascular glenoid articular surfaces suggest affinity with dermochelyoids—the most diverse and geographically widespread clade of Mesozoic chelonioids. The Miria Formation chelonioid scapula constitutes the first definitive record of a Late Cretaceous sea turtle from Australia and is one of the few occurrences thus far documented from Upper Cretaceous–Paleogene deposits in the Southern Hemisphere.

The Oldest African Eucryptodiran Turtle from the Cretaceous of Angola

A new Late Cretaceous turtle, Angolachelys mbaxi gen. et sp. nov., from the Turonian (90 Mya) of Angola, represents the oldest eucryptodire from Africa. Phylogenetic analysis recovers Angolachelys mbaxi as the sister taxon of Sandownia harrisi from the Aptian of Isle of Wight, England. An unnamed turtle from the Albian Glen Rose Formation of Texas (USA) and the Kimmeridgian turtle Solnhofia parsonsi (Germany), are successively more distant sister taxa. Bootstrap analysis suggests those four taxa together form a previously unrecognized monophyletic clade of marine turtles, herein named Angolachelonia clade nov., supported by the following synapomorphies: mandibular articulation of quadrate aligned with or posterior to the occiput, and basisphenoid not visible or visibility greatly reduced in ventral view. Basal eucryptodires and angolachelonians originated in the northern hemisphere, thus Angolachelys represents one of the first marine amniote lineages to have invaded the South Atlantic after separation of Africa and South America.

Recognition of vertebrate egg abnormalities in the Upper Cretaceous fossil record

In fossil vertebrate eggs, the most commonly reported abnormality consists of an unusually thick shell with one or more superimposed eggshell layers. Although rare, taxonomically referable abnormal specimens provide a more reliable basis for inferences regarding reproductive biology of extinct taxa. Eggshell abnormalities recognized in a Cretaceous turtle and three dinosaurs (hadrosaur, sauropod, theropod) are assigned to these taxa base on: 1) normal eggs containing embryos within the same clutch, 2) identical eggshell microstructure as eggs containing embryonic remains from the same stratum; and 3) inclusion of normal eggs of the same oospecies in a cladistic analysis of egg characters. Distinguishing multiple eggshell layers of biological origin from those produced by taphonomic processes is a critical component in the study of fossil specimens. Features useful for distinguishing a pathological condition in fossil eggs include: 1) multiple eggshell layers separated by permineralized membrane, 2) close conformation of the base of the outer eggshell to the unweathered surface of the underlying egg, and 3) structural relationships of eggshell features (e.g. pore truncation, intercalated membrane and shell fragments, optical continuity of superimposed fragments). Documentation of microstructural features of abnormal eggshell provides important information on the timing and magnitude of stress and facilitates recognition of phylogenetically significant patterns of egg abnormality in the fossil record.

A Late Cretaceous (Turonian–Coniacian) high-latitude turtle assemblage from the Canadian Arctic

Three turtles are present in a Turonian–Coniacian age high-latitude vertebrate assemblage from Axel Heiberg Island: Borealochelys axelheibergensis gen. et sp. nov., a generically indeterminate eucryptodire, and a trionychid. The assemblage differs from most Late Cretaceous turtle assemblages from North America in that members of the Paracryptodira are absent. The absence of this group is interpreted as a result of latitudinal differentiation of turtle assemblages in North America during the Late Cretaceous. The level of diversity of turtles in the Axel Heiberg assemblage is comparable to that of mid-latitude assemblages associated with a mean annual paleotemperature of 14 °C, adding to the evidence for high mean annual temperatures at high latitudes during Turonian–Coniacian times.

A New Lindholmemydid Genus (Testudines: Lindholmemydidae) from the Mid-Cretaceous of Uzbekistan

The monotypic Khodzhakulemys gen. nov. is erected to include Mongolemys occidentalis Nessov, 1984, from the Khodzhakul Formation (upper Albian – lower Cenomanian), Khodzhakulsai, Sheikhdzheili and Khodzhakul localities, Uzbekistan. New genus is distinguished from Mongolemys by stronger developed buttresses and presence of nuchal emargination. By degree of development of buttresses Khodzhakulemys occupies transitional position between Mongolemys and Lindholmemys . Phylogenetic relationships of Khodzhakulemys could not be determined with certainty, due to scarce material on this genus. Presence of different genera of lindholmemydids in the late Cretaceous of Middle Asia ( Khodzhakulemys , Lindholmemys ) and Mongolia ( Mongolemys , Gravemys , Hongilemys ) emphasizes peculiarities of these late Cretaceous turtle faunas.