Skull of Procolpochelys grandaeva, USNM 358862, from the lower Miocene...

The extinct marine megafauna of the Phanerozoic

Article

Full-text available

May 2024

The modern marine megafauna is known to play important ecological roles and includes many charismatic species that have drawn the attention of both the scientific community and the public. However, the extinct marine megafauna has never been assessed as a whole, nor has it been defined in deep time. Here, we review the literature to define and list the species that constitute the extinct marine megafauna, and to explore biological and ecological patterns throughout the Phanerozoic. We propose a size cut-off of 1 m of length to define the extinct marine megafauna. Based on this definition, we list 706 taxa belonging to eight main groups. We found that the extinct marine megafauna was conspicuous over the Phanerozoic and ubiquitous across all geological eras and periods, with the Mesozoic, especially the Cretaceous, having the greatest number of taxa. Marine reptiles include the largest size recorded (21 m; Shonisaurus sikanniensis ) and contain the highest number of extinct marine megafaunal taxa. This contrasts with today’s assemblage, where marine animals achieve sizes of >30 m. The extinct marine megafaunal taxa were found to be well-represented in the Paleobiology Database, but not better sampled than their smaller counterparts. Among the extinct marine megafauna, there appears to be an overall increase in body size through time. Most extinct megafaunal taxa were inferred to be macropredators preferentially living in coastal environments. Across the Phanerozoic, megafaunal species had similar extinction risks as smaller species, in stark contrast to modern oceans where the large species are most affected by human perturbations. Our work represents a first step towards a better understanding of the marine megafauna that lived in the geological past. However, more work is required to expand our list of taxa and their traits so that we can obtain a more complete picture of their ecology and evolution.

Paleogene turtles of Eastern Europe: new findings and a revision

Article

Sep 2023

The article provides an overview of all known 39 localities of the Paleogene turtles of Eastern Europe. Numerous remains of turtles are described for the first time from 19 localities, of which six are new, and 13 are the localities from which materials were only mentioned previously. Among them are Pan-Trionychidae indet., Pan-Cheloniidae indet., Dermochelyidae indet. and Pan-Testudines indet., as well as pan-cheloniids Argillochelys sp. from the Ypresian Novoivanovka and the Ypresian or Lutetian Gruzinov localities. Several indeterminate specimens from Eocene localities show similarity to pan-cheloniids Argillochelys cuneiceps (Owen, 1849) and Puppigerus camperi (Gray, 1831) or Tasbacka aldabergeni Nessov, 1987, and dermochelyids Natemys peruvianus Wood et al., 1996 or “Psephophorus” rupeliensis van Beneden, 1883. One specimen of costal 1 of Pan-Testudines indet. from the Lutetian Krasnorechenskoe locality resembles that of pleurodires Eocenochelus spp. and Neochelys spp. In addition, new materials of turtles are described from five previously known localities. Among them, new and additionally restored specimens from the Bartonian Ak-Kaya 1 locality of the pan-cheloniid Argillochelys sp., and the dermochelyid Cosmochelys sp., which expand data on their morphology and intraspecific variability. The specimens of pan-cheloniids with deep and dense sculpturing of the external shell surface from the Bakhmutovka, Bulgakovka, Krasnorechenskoe and Tripolye localities clearly belong to a new species, not described due to fragmentary material. It is supposed that Anhuichelys-like pan-testudinoids migrated from Asia in Eastern Europe in the Danian age, and were preserved as relict Dithyrosternon valdense Pictet et Humbert, 1855 until the Priabonian age.

The Geology and Vertebrate Paleontology of Calvert Cliffs, Maryland, USA - Volume 2: Turtles and Toothed Whales

Book

Aug 2023

This volume is a follow-on to a work published by Smithsonian Institution Scholarly Press in 2018 on the Miocene vertebrate fauna from Calvert Cliffs, Maryland, USA. Two chapters are included in this compendium, one on turtles (chelonians) and the other on toothed whales (odontocetes). It is anticipated that two more volumes will be needed to complete the taxonomic review. Robert E. Weems details the occurrence of 19 kinds of chelonians that have been discovered in the Miocene and Pliocene marine strata of Delaware, Maryland, and Virginia, USA, 13 of them in the Calvert Cliffs. The most commonly found remains are those of an extinct sea turtle, Trachyaspis lardyi. Remains of four other marine turtles, Procolpochelys grandaeva, Lepidochelys sp., a generically indeterminate cheloniid, and a leatherback turtle (Psephophorus polygonus), are far less common. The other 14 chelonian taxa are nonmarine forms that inhabited the land, rivers, and marshes west of the Mid-Atlantic Seaboard during the Miocene. They were washed into the coastal marine environments that were then accumulating the sediments exposed today as the strata in the Calvert Cliffs. Stephen J. Godfrey and Olivier Lambert review the taxonomically diverse odontocete fauna of 29 named species. Nine of these Miocene taxa represent newly named species. Fragmentary remains hint at even greater diversity. Reviewed taxa are restricted to those known from along the Calvert Cliffs and other Miocene age deposits on the Atlantic Coastal Plain in Maryland and Virginia, USA. They range in age from approximately 22 to 8 Ma and derive from the Calvert, Choptank, and St. Marys Formations. This fauna preserves one of the most abundant and diverse assemblages of extinct toothed whales known. None of the named odontocete species included in this review are known from beyond the North Atlantic Ocean. In terms of their chronostratigraphic distribution, collectively, they range in age from the Aquitanian through the Tortonian, with the large majority occurring within the Burdigalian, Langhian, and Serravallian stages (the latter two being the most speciose). The greatest taxonomic diversity occurred during the Miocene Climate Optimum, a time (ca. 17–15 Ma) when global average temperatures were as much as 4°C to 5°C above today’s average temperatures, at least for much of that interval.

Miocene Toothed Whales (Odontoceti) from Calvert Cliffs, Atlantic Coastal Plain, USA

Article

Aug 2023

A taxonomically diverse toothed whale (Cetacea, Odontoceti) fauna of 29 named species is known from along the Calvert Cliffs and other Miocene age deposits (Chesapeake Group) within the Chesapeake Bay region (Atlantic Coastal Plain, Maryland and Virginia, USA). They range in age from approximately 22 to 8 Ma and derive from the Calvert, Choptank, and St. Marys Formations. Representatives of the following families are known: Squalodontidae, Physeteridae, Ziphiidae, Squalodelphinidae, Platanistidae, Eurhinodelphinidae, Kentriodontidae, Pontoporiidae, and basal delphinidans formerly placed within Kentriodontidae. Four of these families have living representatives: Physeteridae, Ziphiidae, Platanistidae, and Pontoporiidae. Squalodontidae is represented by three species: Squalodon calvertensis, S. whitmorei, and S. murdochi sp. nov. Physeteridae includes Orycterocetus crocodilinus and “Aulophyseter” mediatlanticus. Ziphiidae includes two unnamed species: cf. Messapicetus sp. and Ziphiidae incertae sedis. Squalodelphinidae is known by at least two species: Phocageneus venustus and an undetermined species. Platanistidae is represented by five species: Araeodelphis natator, Grimadelphis spectorum gen. et sp. nov., Zarhachis flagellator, Pomatodelphis inaequalis, and Pomatodelphis santamaria sp. nov. Eurhinodelphinidae features at least four species: Xiphiacetus bossi, X. cristatus, Schizodelphis barnesi, and S. morckhoviensis. Kentriodontidae includes Kentriodon pernix. Other Miocene delphinidans (most of which have previously been included within the Kentriodontidae) include Brevirostrodelphis dividum (new combination), Hadrodelphis calvertense, Macrokentriodon morani, Miminiacetus pappus (new combination), Pithanodelphis cornutus (recognized here from the Atlantic Coastal Plain for the first time), Lophocetus calvertensis, and four new delphinidans: Herbeinodelphis nancei gen. et sp. nov., Cammackacetus hazenorum gen. et sp. nov., Pictodelphis kidwellae gen. et sp. nov., and Westmorelandelphis tacheroni gen. et sp. nov. Pontoporiidae is represented by a single named species, Stenasodelphis russellae. Odontoceti incertae sedis includes a Chilcacetus-grade odontocete, Caolodelphis milleri gen. et sp. nov., the puzzling Enigmatocetus posidoni gen. et sp. nov., and other partial skulls. Sixty-two percent of the Miocene odontocetes from Maryland and Virginia are endemic to this region, and 83% are known only from the western North Atlantic. In terms of their chronostratigraphic distribution, collectively, they range in age from Aquitanian through Tortonian, with the large majority occurring within the Burdigalian, Langhian, and Serravallian stages.

A gar-bitten vertebrate coprolite from the Neogene of the Atlantic Coastal Plain, USA, and a new ichnospecies of Machichnus Mikuláš et al., 2006

Article

Full-text available

Mar 2023
Ichnos

Vertebrate-bitten coprolites are seemingly rare; nonetheless, within the past dozen years, a handful of these composite trace fossils have been found and described. Here, we describe a single crocodile coprolite from the Lower Miocene Calvert Formation in New Kent County, Virginia, USA, showing bite marks. The size and morphology of the coprolite is consistent with a crocodilian origin. Seven parallel, gently curving gouges, of biogenic origin, disrupt the surface of the coprolite. As it is a medium preserving bite marks, this coprolite qualifies as a morderolite. Furthermore, because of the presence of larger/deeper primary, and finer secondary gouges, which we interpreted as individual tooth marks, the identity of the vertebrate that bit the coprolite is most likely gar (Lepisosteidae). Because other comparable coprolites preserving similar sets of primary and secondary gouges are known, this unique trace fossil is given a new ichnotaxonomic name, Machichnus dimorphodon isp. nov. Many more much smaller markings, interpreted as feeding traces by smaller organisms (possibly invertebrates) also ornament the surface of the coprolite.

Ghosts of the Holobiont: Borings on a Miocene Turtle Carapace from the Pisco Formation (Peru) as Witnesses of Ancient Symbiosis

Article

Full-text available

Dec 2022

In spite of the widespread occurrence of epibiotic turtle barnacles (Coronuloidea: Chelonibiidae and Platylepadidae) on extant marine turtles (Chelonioidea: Cheloniidae and Dermochelyidae), and although the association between these cirripedes and their chelonian hosts has existed for more than 30 million years, only a few studies have investigated the deep past of this iconic symbiotic relationship on palaeontological grounds. We describe probable platylepadid attachment scars in the form of hemispherical/hemiellipsoidal borings on an Upper Miocene (Tortonian) fragmentary turtle carapace, identified herein as belonging to Cheloniidae, from the Pisco Lagerstätte (East Pisco Basin, southern Peru). When coupled with the available molecular data, this and other similar ichnofossils allow for hypothesising that platylepadid symbionts were hosted by sea turtles as early as in early Oligocene times and became relatively widespread during the subsequent Miocene epoch. Chelonian fossils that preserve evidence of colonisation by platylepadid epibionts in the form of pits on the turtle shell should be regarded as fossil holobionts, i.e., palaeontological witnesses of discrete communal ecological units formed by a basibiont and the associated symbionts (including the epibiota). A greater attention to the bone modifications that may be detected on fossil turtle bones is expected to contribute significantly to the emerging field of palaeosymbiology.

2022 Zonneveld-etal Caretta-caretta

Article

Nov 2022

Sea turtles are characterized by a wide variety of invertebrate ectoparasites. Few of these ectoparasites leave a permanent indication of their presence on the skeletal remains of their host taxa and thus represent ecological information doomed to be lost in the paleontological record. Some barnacle taxa provide an exception to this, in that they cause the formation of small, subcircular to circular divots, pits, and holes on the skull, mandible, carapace or plastron of sea turtles. Loggerhead Sea Turtle (Caretta caretta) skeletons from Cumberland Island, Georgia, USA were examined to assess the presence, frequency, and loci of occurrence of barnacle pits, and to establish which taxa are involved in pit development. Six types of divot and pit attributed to barnacles are identiﬁed in this study. Type I traces are shallow, oval/semi-circular in outline, with smooth, gently sloped bases. Type II traces are deep, hemispherical pits with smooth bases. Type III traces are deep, circular to subcircular pits with ﬂat bases. Type IV traces are deep, circular to subcircular pits with multiple (4–6) small sub-pits on their bases. Type V traces are cylindrical, penetrative holes. Type VI traces comprise shallow ring-shaped grooves on the surface of the bone. Type I through III traces are identical to the ichnotaxon Karethraichnus lakkos. Type IV traces have not, as yet, been described in the rock record. Type V traces are identical to K. ﬁale. Type VI traces are identical to Thatchtelithichnus holmani.Barnacletaxaidentiﬁedas emplacing non-penetrative divots and pits on C. caretta skulls, mandibles, and shell bones include Chelonibia caretta (Type I), Platylepas hexastylos (Types I–IV), Calyptolepas bjorndalae (Types I and II), and Stomatolepas elegans (Types I and II). Type V traces were most likely emplaced by either Stephanolepas muricata or Chelolepas cheloniae. Type VI traces reﬂect the former attachment of balanid or lepadid barnacles. Embedded barnacles were observed in epidermal material associated with Types I through IV traces but not for Type V and VI traces and thus the relationship is inferred for these latter traces. Barnacle-related pits, divots, and holes are believed to result from barnacle mediated chemical corrosion into the outer surface of sea turtle bone. The occurrence of these traces provides one of the few preservable lines of evidence of barnacle interactions with sea turtle hosts. Identiﬁcation of deﬁnitive barnacle borings in fossil material will provide evidence of the evolution of platylepadid barnacles and the development of their commensal relationship with chelonid turtles.

BONE MODIFICATION FEATURES RESULTING FROM BARNACLE ATTACHMENT ON THE BONES OF LOGGERHEAD SEA TURTLES ( Caretta caretta ), CUMBERLAND ISLAND, GEORGIA, USA: IMPLICATIONS FOR THE PALEOECOLOGICAL, AND TAPHONOMIC ANALYSES OF FOSSIL SEA TURTLES

Article

Nov 2022
PALAIOS

Sea turtles are characterized by a wide variety of invertebrate ectoparasites. Few of these ectoparasites leave a permanent indication of their presence on the skeletal remains of their host taxa and thus represent ecological information doomed to be lost in the paleontological record. Some barnacle taxa provide an exception to this, in that they cause the formation of small, subcircular to circular divots, pits, and holes on the skull, mandible, carapace or plastron of sea turtles. Loggerhead Sea Turtle (Caretta caretta) skeletons from Cumberland Island, Georgia, USA were examined to assess the presence, frequency, and loci of occurrence of barnacle pits, and to establish which taxa are involved in pit development. Six types of divot and pit attributed to barnacles are identified in this study. Type I traces are shallow, oval/semi-circular in outline, with smooth, gently sloped bases. Type II traces are deep, hemispherical pits with smooth bases. Type III traces are deep, circular to subcircular pits with flat bases. Type IV traces are deep, circular to subcircular pits with multiple (4–6) small sub-pits on their bases. Type V traces are cylindrical, penetrative holes. Type VI traces comprise shallow ring-shaped grooves on the surface of the bone. Type I through III traces are identical to the ichnotaxon Karethraichnus lakkos. Type IV traces have not, as yet, been described in the rock record. Type V traces are identical to K. fiale. Type VI traces are identical to Thatchtelithichnus holmani. Barnacle taxa identified as emplacing non-penetrative divots and pits on C. caretta skulls, mandibles, and shell bones include Chelonibia caretta (Type I), Platylepas hexastylos (Types I–IV), Calyptolepas bjorndalae (Types I and II), and Stomatolepas elegans (Types I and II). Type V traces were most likely emplaced by either Stephanolepas muricata or Chelolepas cheloniae. Type VI traces reflect the former attachment of balanid or lepadid barnacles. Embedded barnacles were observed in epidermal material associated with Types I through IV traces but not for Type V and VI traces and thus the relationship is inferred for these latter traces. Barnacle-related pits, divots, and holes are believed to result from barnacle mediated chemical corrosion into the outer surface of sea turtle bone. The occurrence of these traces provides one of the few preservable lines of evidence of barnacle interactions with sea turtle hosts. Identification of definitive barnacle borings in fossil material will provide evidence of the evolution of platylepadid barnacles and the development of their commensal relationship with chelonid turtles.

Turtle barnacles have been turtle riders for more than 30 million years

Article

Full-text available

Oct 2022

In contrast to other kinds of biological interactions, symbiosis is a scarcely investigated aspect of the fossil record. This is largely due to taphonomic biases that often frustrate any attempt to make a strong case that two organisms shared an intimate association in life. Among extant marine vertebrates, the sea turtles (Cheloniidae and Dermochelyidae) bear a broad and diverse spectrum of epibiotic symbionts, including specialists such as the turtle barnacles (Chelonibiidae and Platyleapa-didae). Here, we reappraise an early Oligocene (Rupelian) fossil cheloniid skeleton, featuring the remains of cirripedes on the exterior of its entoplastron, from the Rauenberg fossil-lagerstätte, southwestern Germany. The barnacle specimens are assigned to Protochelonibia melleni, an extinct protochelonibiine species and the geologically oldest known member of Chelonibiidae. In the light of taphonomic and palaeoenvironmental considerations, and given that the extant chelonibiids are mostly known as epizoic symbionts of sea turtles, we conclude that this unique fossil association resulted from the epizoic growth of the barnacles on the external surface of the plastron of the turtle during its lifetime. This remarkable fossil association provides evidence that chelonibiids, including the extinct protochelonibiines, have been chelonophilic epizoans for more than 30 Myr. A survey of the trace and body fossil records shows that platylepadids are also likely as old as the Rupelian as is their symbiotic association with cheloniid hosts. This early emergence of the modern-looking, turtle-dwelling barnacle lineages corresponds to a climate-driven phase of major radiation and taxonomic turnover among sea turtles at the Eocene-Oligocene transition.

A Late Cretaceous Sea Turtle from Bentiaba, Angola ascribed to Euclastes

Thesis

Jul 2022

Gonçalo Soares

The locality of Bentiaba, in the Namibe Basin, Angola, is one of the richest and most diverse fossiliferous outcrops of the Southern Hemisphere regarding marine vertebrates, with the expeditions from the Project PaleoAngola recovering various taxa such as bony fishes, sharks, mosasaurs, plesiosaurs, pterosaurs, and sea turtles. Here I reported a new specimen of a stem cheloniid recovered from the Lower Maastrichtian of Bentiaba, consisting of post-cranial remains, including the shell, plastron, more than ten vertebrae, one coracoid, and one metatarsal bone. Phylogenetic analysis places the Bentiaba specimen within Euclastes, but morphological comparison with Euclastes postcranial reveals differences. Euclastes was previously reported to Bentiaba, based on skull and postcranial material, but without any species attribution. The phylogenetic analysis resulted in various unexpected results, such as the placement of presumed cheloniids, such as Eochelone brabantica and Procolpochelys grandaeva as stem-dermochelyids, Ctenochelys stenoporus placed outside of Ctenochelyidae, and instead inserted in a polytomy with the aberrant chelonioid Allopleuron hofmanni and the dubious taxon Lophochelys, and placing Protostegidae and Angolachelonia within Chelonioidea, nesting Angolachelonia as sister taxon with Stem-Cheloniidae.

Skull of Procolpochelys grandaeva, USNM 358862, from the lower Miocene of Maryland. A, left lateral, B, posterior, C, dorsal, and D, ventral views. In B a clayball is visible holding the skull roof in its correct relative position to the basicranium.

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