Global ecomorphological restructuring of dominant marine reptiles prior to the K/Pg mass extinction

Mosasaurid squamates were the dominant amniote predators in marine ecosystems during most of the Late Cretaceous. Evidence from multiple sites worldwide of a global mosasaurid community restructuring across the Campanian-Maastrichtian transition may have wide-ranging implications for the evolution of diversity of these top oceanic predators. In this study, we use a suite of biomechanical traits and functionally descriptive ratios to investigate how the morphofunctional disparity of mosasaurids evolved through time and space prior to the Cretaceous-Palaeogene (K/Pg) mass extinction. Our results suggest that the worldwide taxonomic turnover in mosasaurid community composition from Campanian to Maastrichtian is reflected by a notable increase in morphofunctional disparity on a global scale, but especially driven the North American record. Ecomorphospace occupation becomes more polarised during the late Maastrichtian, as the morphofunctional disparity of mosasaurids plateaus in the Southern Hemisphere and decreases in the Northern Hemisphere. We show that these changes are not associated with strong modifications in mosasaurid size, but rather with the functional capacities of their skulls, and that mosasaurid morphofunctional disparity was in decline in several provincial communities before the K/Pg mass extinction. Our study highlights region-specific patterns of disparity evolution, and the importance of assessing vertebrate extinctions both globally and regionally. Ecomorphological differentiation in mosasaurid communities, coupled with declines in other formerly abundant marine reptile groups, indicates widespread restructuring of higher trophic levels in marine food webs was well underway when the K-Pg mass extinction took place.

Tooth Structure and Replacement of the Triassic Keichousaurus (Sauropterygia, Reptilia) From South China

The small-sized sauropterygian Keichousaurus hui was one of the most abundant marine reptiles from the Triassic Yangtze Sea in South China. Although Keichousaurus has been studied in many aspects, including the osteology, ontogeny, sexual dimorphism, and reproduction, the dentition of this marine reptile was only briefly described in external morphology. In this study, we provide new information on Keichousaurus tooth implantation, histology, and replacement based on a detailed examination of well-preserved specimens collected in the past decades. The tooth histology has been investigated for the first time by analyzing cross-sections of premaxillary teeth and the tooth attachment and implantation have been further revealed by X-ray computed microtomography. We refer the tooth replacement of Keichousaurus to the iguanid replacement type on the basis of the observed invasion of small replacement tooth into the pulp cavity of the functional tooth. Given the resemblance to other extinct and modern piscivorous predators in the morphology and structure of teeth, Keichousaurus might mainly feed on small or juvenile fishes and some relatively soft-bodied invertebrates (e.g., mysidacean shrimps) from the same ecosystem.

Triassic marine reptiles and other fossil vertebrates from the area of Godech, Western Bulgaria

Hitherto, the popular understanding was that the Bulgarian fossil record of Mesozoic tetrapods (four-limbed vertebrates) has been restricted to the Upper Cretaceous. In this contribution we report on the discovery of isolated bones of marine reptiles and teeth of various vertebrates from the Middle Triassic carbonate rocks outcropping near the town of Godech, Western Bulgaria. A revision of the currently held orthodoxy that Bulgaria is mostly a barren land when it comes to Mesozoic tetrapods is urged.

An injured pachypleurosaur (Diapsida: Sauropterygia) from the Middle Triassic Luoping Biota indicating predation pressure in the Mesozoic

The Middle Triassic Luoping Biota in south-west China represents the inception of modern marine ecosystems, with abundant and diverse arthropods, fishes and marine reptiles, indicating recovery from the Permian–Triassic mass extinction. Here we report a new specimen of the predatory marine reptile Diandongosaurus, based on a nearly complete skeleton. The specimen is larger than most other known pachypleurosaurs, and the body shape, caniniform teeth, clavicle with anterior process, and flat distal end of the anterior caudal ribs show its affinities with Diandongosaurus acutidentatus, while the new specimen is approximately three times larger than the holotype. The morphological characters indicate that the new specimen is an adult of D. acutidentatus, allowing for ontogenetic variation. The fang-like teeth and large body size confirm it was a predator, but the amputated hind limb on the right side indicate itself had been predated by an unknown hunter. Predation on such a large predator reveals that predation pressure in the early Mesozoic was intensive, a possible early hint of the Mesozoic Marine Revolution.

The locomotory apparatus and paraxial swimming in fossil and living marine reptiles: comparing Nothosauroidea, Plesiosauria, and Chelonioidea

The terrestrial origins of the diapsid Sauropterygia and Testudines are uncertain, with the latter being highly controversially discussed to this day. For only 15 Ma, Nothosauroidea lived in shallow-marine seas of the Triassic. Contrastingly, the pelagic Plesiosauria evolved in the Late Triassic, dispersed globally, and inhabited the oceans of the Jurassic and Cretaceous for approximately 135 Ma. Since the Cretaceous (~ 100 Ma), Chelonioidea, the modern sea turtles, have populated the oceans. All three groups evolved aquatic paraxial locomotion. Nothosaurs swam with their foreflippers, supported by the swimming tail. Plesiosaurs are the only tetrapods to have ever evolved four hydrofoil-like flippers. The plesiosaur flipper beat cycle has been debated for nearly two centuries. The different proposed locomotory styles (rowing, rowing-flight, underwater flight) are discussed in this review. A fourth gait that is employed by Carettochelys insculpta, which combines rowing and flying, is introduced. The osteology of the locomotory apparatus of nothosaurs and plesiosaurs is reviewed and compared to that of extant underwater-flying Chelonioidea. In conclusion, underwater flight remains the favoured locomotory style for plesiosaurs. Also, the review reveals that nothosaur locomotion has largely remained unstudied. Further, our understanding of joint morphologies and mobilities of the foreflipper in nothosaurs, plesiosaurs, and even recent sea turtles, and of the hindflipper in plesiosaurs, is very limited. It is crucial to the discussion of locomotion, to find out, if certain limb cycles were even possible, as evidence seems to point to the improbability of a rowing motion because of limited humerus and femur long axis rotation in plesiosaurs.

Incorporating wildlife effectively into oil spill exercises – An Australian Story

Australia holds regular National oil spill exercises through the National Plan for Maritime Emergencies. Two National Plan exercise activities that have taken place include Exercise Northerly held in Darwin (Northern Territory) in 2014 and Exercise Torres focussed on the Torres Straits (Queensland) in 2018. The overall aim of the two exercises were to implement and review the effectiveness of a combined Commonwealth (Federal), Territory/State and industry marine pollution response to a Level 3 pollution incident. Both Exercise Northerly and Exercise Torres included oiled wildlife response actions to practice and test. Exercise Northerly for wildlife was principally a desk top activity that included a number of injects relating to wildlife threatened and impacted by an oil spill event. Wildlife considered in Northerly included cetaceans, dugong, marine reptiles and seabirds. The key wildlife objectives for Northerly were to establish and maintain a wildlife Incident Management Team under the broader Incident Command structure and develop wildlife incident action plans for hazing wildlife and responding to oil impacted wildlife. Exercise Torres incorporated both planning and field based operational activities and considered cetaceans, dugong, marine reptiles and seabirds both threatened and impacted by oil pollution. Wildlife planning during exercise Torres was principally held in Cairns at the established Incident Control Centre where incident action plans were developed to haze oil threatened wildlife, collect oiled impacted wildlife and then rehabilitate wildlife considering the strict quarantine restrictions imposed on wildlife movements through and out of the Torres Strait Protection Zone. The field deployment activities for Torres were then managed and undertaken through a forward operations base established on Waiben Island, some 800 kilometres or 500 miles north of Cairns that borders Papua New Guinea. The wildlife field teams were required to establish an oiled wildlife response centre making it fully operational with pre-deployed equipment, manage responder safety for actual dangerous wildlife in the area, respond to reports of impacted wildlife, transport impacted mock wildlife through the different contaminant hazard zones (i.e. hot, warm and cold zones) and then to the wildlife care centre, undertake wildlife assessment using narrative techniques, triage wildlife based on provided wildlife assessment data, decontaminate mock wildlife and then provide basic wildlife rehabilitation practices. Both of the National exercises provided effective opportunities to practice the skills necessary to support oiled wildlife response actions and to identify key learnings for better practices when responding to oiled wildlife threatened and impacted in remote areas.

A regurgitalite of the Middle Triassic (Muschelkalk) from Upper Silesia (Poland)

A bromalite from the Middle Triassic (Muschelkalk) of southern Poland, Sadowa Góra Quarry, is herein described and interpreted as a regurgitalite. The fossils occurring within the regurgitalite are angular and have sharp edges. They are represented by common fragments of thin-shelled bivalves as well as rare crinoid and gastropod remains. The composition of the collected inclusion is different from that of the host rock. There are many candidates that could have produced the regurgitalite, including durophagous sharks, marine reptiles, the actinopterygian Colobodus, or nautiloids. Our finding adds to the emerging evidence of durophagous predation in the Triassic sea of Polish part of the Germanic Basin. It is the second record of a regurgitalite from the Muschelkalk of Upper Silesia.