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[dinosaur] Turtle plastron growth + new fossil crocodylians + new plotopterids + dung-eating beetles + more

Ben Creisler


Some recent non-dino papers that may be of interest:

Ritva Rice, Aki Kallonen, Judith Cebra-Thomas, and Scott F. Gilbert (2016)

Development of the turtle plastron, the order-defining skeletal structure.

Proceedings of the National Academy of Sciences (advance online publication)

doi: 10.1073/pnas.1600958113





The plastron, the order-defining skeletal structure for turtles, provides a bony exoskeleton for the ventral side of the turtle. We provide here the first molecular analysis of plastron bone formation. We show that plastron bone morphogenesis in the ventral mesenchyme employs a program of bone formation that usually characterizes the vertebrate face and skull. The plastron bones, however, have a preliminary step that is not included in head formation: They must suppress the usual chondrogenic programs that would create the sternum cartilage. We suggest that the early osteogenic fate adopted by the ventral mesenchyme prevents the chondrogenic sternal development in turtles and that this was a critical step in forming the ossification centers for this new type of vertebrate structure.



The dorsal and ventral aspects of the turtle shell, the carapace and the plastron, are developmentally different entities. The carapace contains axial endochondral skeletal elements and exoskeletal dermal bones. The exoskeletal plastron is found in all extant and extinct species of crown turtles found to date and is synaptomorphic of the order Testudines. However, paleontological reconstructed transition forms lack a fully developed carapace and show a progression of bony elements ancestral to the plastron. To understand the evolutionary development of the plastron, it is essential to know how it has formed. Here we studied the molecular development and patterning of plastron bones in a cryptodire turtle Trachemys scripta. We show that plastron development begins at developmental stage 15 when osteochondrogenic mesenchyme forms condensates for each plastron bone at the lateral edges of the ventral mesenchyme. These condensations commit to an osteogenic identity and suppress chondrogenesis. Their development overlaps with that of sternal cartilage development in chicks and mice. Thus, we suggest that in turtles, the sternal morphogenesis is prevented in the ventral mesenchyme by the concomitant induction of osteogenesis and the suppression of chondrogenesis. The osteogenic subroutines later direct the growth and patterning of plastron bones in an autonomous manner. The initiation of plastron bone development coincides with that of carapacial ridge formation, suggesting that the development of dorsal and ventral shells are coordinated from the start and that adopting an osteogenesis-inducing and chondrogenesis-suppressing cell fate in the ventral mesenchyme has permitted turtles to develop their order-specific ventral morphology.


Free pdf:

Rodolfo Salas-Gismondi , John J. Flynn, Patrice Baby, Julia V. Tejada-Lara, Julien Claude, Pierre-Olivier Antoine  (2016)

A New 13 Million Year Old Gavialoid Crocodylian from Proto-Amazonian Mega-Wetlands Reveals Parallel Evolutionary Trends in Skull Shape Linked to Longirostry.

PLoS ONE 11(4): e0152453.



Gavialoid crocodylians are the archetypal longirostrine archosaurs and, as such, understanding their patterns of evolution is fundamental to recognizing cranial rearrangements and reconstructing adaptive pathways associated with elongation of the rostrum (longirostry). The living Indian gharial Gavialis gangeticus is the sole survivor of the group, thus providing unique evidence on the distinctive biology of its fossil kin. Yet phylogenetic relationships and evolutionary ecology spanning ~70 million-years of longirostrine crocodylian diversification remain unclear. Analysis of cranial anatomy of a new proto-Amazonian gavialoid, Gryposuchus pachakamue sp. nov., from the Miocene lakes and swamps of the Pebas Mega-Wetland System reveals that acquisition of both widely separated and protruding eyes (telescoped orbits) and riverine ecology within South American and Indian gavialoids is the result of parallel evolution. Phylogenetic and morphometric analyses show that, in association with longirostry, circumorbital bone configuration can evolve rapidly for coping with trends in environmental conditions and may reflect shifts in feeding strategy. Our results support a long-term radiation of the South American forms, with taxa occupying either extreme of the gavialoid morphospace showing preferences for coastal marine versus fluvial environments. The early biogeographic history of South American gavialoids was strongly linked to the northward drainage system connecting proto-Amazonian wetlands to the Caribbean region.



Stéphane Jouve (2016)

A new basal tomistomine (Crocodylia, Crocodyloidea) from Issel (Middle Eocene; France): palaeobiogeography of basal tomistomines and palaeogeographic consequences.

Zoological Journal of the Linnean Society 177(1): 165–182

DOI: 10.1111/zoj.12357



A skull and mandible of a crocodylian from the late Lutetian of Issel, previously described as ‘Atacisaurus glareae’ is reconsidered. The holotype of ‘A. glareae’, a partial mandible, is lost, and the skull cannot be designated as a lectotype for the species. ‘Atacisaurus glareae’ is thus a nomen dubium. The skull bears a combination of characters, allowing us to assign it to the genus Kentisuchus. It differs from the, until now, only known species Kentisuchus spenceri from the Ypresian of England, in having a more robust snout, with the constriction of the snout at the level of the seventh–eighth teeth being 80% of the largest maxillary width, and not bearing anteroposterior shallow fossae along the lacrimomaxillary sutures. A new species is thus erected, Kentisuchus astrei sp. nov. Phylogenetic analysis confirms that the genus Kentisuchus is one of the most primitive tomistomine. The phylogenetic and palaeogeographic distribution suggests that Kentisuchus was isolated in the Atlantic Ocean, and Ebro (Spain) and Aquitaine (France) basins, during the Ypresian, and that the south Pyrenean marine corridor between the Atlantic Ocean and the Tethys could have closed during the early Ypresian, earlier than previously supposed. This could be correlated with the first mammal migrations from the Iberian Peninsula to Southern France. The palaeogeographic distribution of early and middle Eocene tomistomines also suggests the possible presence of a marine corridor between the North Sea and the Central Tethys through the Polish Lowlands Basin during the early Lutetian. This marine corridor could be informative for studies on mammal migration, as the presence of a north–south marine corridor necessarily means there is an absence or less efficient east–west terrestrial passage. This could have consequences on the history of Asian–European mammal migrations.



Gerald Mayr & James L. Goedert (2016)

New late Eocene and Oligocene remains of the flightless, penguin-like plotopterids (Aves, Plotopteridae) from western Washington State, U.S.A.

Journal of Vertebrate Paleontology (advance online publication)



We describe new plotopterids (Aves, Plotopteridae) from late Eocene and Oligocene strata in western Washington State, U.S.A. The specimens belong to four new species of these flightless, wing-propelled seabirds, three of which are named and assigned to two new supraspecific taxa, Olympidytes, gen. nov., and Klallamornis, gen. nov. We confirm previous observations on a high diversity of plotopterids in the Paleogene of North America, but because the fossils are from different formations, it remains elusive how many of the six currently recognized species from western Washington actually coexisted. Tonsala, the only previously described plotopterid taxon from the Olympic Peninsula, is likely to occupy a more basal phylogenetic position than the other plotopterids of this geographic area. Olympidytes and Klallamornis may be successive sister taxa of Copepteryx and Hokkaidornis from the late Oligocene of Japan, but a determination of the exact affinities of the new taxa requires the discovery of further fossils. Notably, the geochronologically youngest plotopterid, the early Miocene Plotopterum, differs from earlier taxa in plesiomorphic features and is here considered to be among the phylogenetically most basal plotopterids. The late Eocene basal Phocavis likewise temporally overlaps with more derived plotopterid taxa. The coexistence of basal and more derived plotopterids in the late Eocene may indicate a rapid evolution of plotopterids towards the late Eocene. The factors that allowed the persistence of basal taxa into the Miocene remain, however, elusive, and so are those that triggered the evolution of wing-propelled diving in these highly specialized birds.




Free pdf:

Debra M. Wotton, Donald R. Drake, Ralph G. Powlesland & Jenny J. Ladley (2016)

The role of lizards as seed dispersers in New Zealand.

Journal of the Royal Society of New Zealand 46(1):  40-65

Special Issue:   New Zealand herpetology: Tony Whitaker's legacy.




There is growing awareness globally of the role lizards play as seed dispersers. In New Zealand, it has been suggested that lizards are effective dispersers, and white–blue fruits and divaricating shrubs are adapted to lizard dispersal. We present new data and review the lizard seed dispersal literature. Lizards eat fruits of at least 23 native species, five of which are divaricating. Birds also eat fruits of divaricating species. Lizards prefer white-blue fruits to red fruits, and eat white–blue-fruited species more frequently than expected given their occurrence in the flora. White–blue fruits are associated with divaricating shrubs and open habitats. Seeds in lizard scats have germination percentages ≤ control seeds in four species tested. Lizards generally disperse seeds < 20 m, but allow seeds to escape parent plants and reach safe establishment sites. Lizards can be important seed dispersers even at reduced densities on the mainland, where they may disperse a larger fraction of seeds than previously assumed. In shrublands lacking frugivorous birds, lizards may be the only remaining dispersers.



It started with dinosaurs...

Free pdf:

Peter Holter (2016)

Herbivore dung as food for dung beetles: elementary coprology for entomologists.

Ecological Entomology (advance online publication)

DOI: 10.1111/een.12316


1. How do dung beetles and their larvae manage to subsist on herbivore dung consisting of plant remains that are at least partly indigestible, mixed with various metabolic waste products? To clarify what is known and not known about this basic aspect of dung beetle biology, the present review summarises information on dung composition and discusses the feeding of beetles (food: fresh dung) and larvae (food: older dung) in relation to this information.


2. There is 70–85% water in typical fresh dung, and undigested lignocellulose or ‘fibre’ constitutes about 70% of the organic matter which also contains 1.5–3% N. About 75% of this is ‘metabolic faecal nitrogen’, mostly associated with dead and alive microbial biomass. As all essential amino acids and cholesterol are probably present, additional synthesis by microbial symbionts may not be needed by the beetles.


3. Beetles minimise the intake of lignocellulose by filtering fibre particles out of their food which is probably microbial biomass/debris with much smaller particle size. Excess fluid may be squeezed out of this material by the mandibles before ingestion.


4. All larvae are bulk feeders and unable to filtrate, but little is known about the composition of their food, i.e. older dung in pats or underground brood masses. Larvae in dung pats may depend on easily digestible dung components, probably microbial biomass, whereas the nutritional ecology of larvae in brood masses is still not understood. Unravelling the composition of their food might answer some of the so far unanswered questions.


Triassic Refs List for 2014 (free pdf)

Geoffrey Warrington (2015)

New Triassic literature.

Albertiana 43: 33–65