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[dinosaur] Linderochelys + crocodilian nest taphonomy + Carboniferous tetrapod footprints from Morocco

Ben Creisler

Some recent non-dino papers:

J.M. Jannello, I.J. Maniel, E. Previtera & M.S. de la Fuente (2017)
Linderochelys rinconensis (Testudines: Pan-Chelidae) from the Upper Cretaceous of northern Patagonia: New insights from shell bone histology, morphology and diagenetic implications.
Cretaceous Research (advance online publication)
doi: https://doi.org/10.1016/j.cretres.2017.05.011

The panchelid turtle Linderochelys rinconensis de la Fuente, Calvo and González Riga, 2007 was described on the basis of several postcranial elements from the Rio Neuquén Subgroup of Loma del Lindero site, near Rincon de los Sauces (Neuquén, Argentina). New preparation of the type material revealed new parts of the animal, including cervical vertebrae, parts of the carapace and a right tibia. The study of the newly recovered material herein improves our knowledge of the macroanatomy of this taxon. The first costal shows an axillary buttress similar to Australasian chelids and the cervical vertebrae morphology suggests a short-necked chelid condition. The re-examination of the type material of Linderochelys and the discovery of new material allowed new studies on microanatomy, osteohistology and diagenesis. Osteohistology suggests some similarities with Patagonian Cretaceous and Palaeocene Yaminuechelys, based on the presence of parallel-fibred bone in the external cortex and a much thinner internal cortex. Paleoecological studies on the proportions of forelimbs and microanatomy point towards aquatic or semi-aquatic habits, closely related to the condition seen in some extant South American chelids, such as Phrynops hilarii, Phrynops geoffroanus, and Mesoclemmys gibba. The fossil-diagenetic processes inferred substitution, fracturing, plastic deformation and permineralization events. Combined analyses through scanning electron microscopy with energy-dispersive X-ray spectrometry and petrographic studies revealed the substitution of hydroxyapatite by francolite. Permineralization stages include infilling of vascular canals, trabeculae and fractures with iron oxides and carbonate minerals during their burial history.


Ashley L. Ferguson, David J. Varricchio, Carlos I. Piña & Frankie D. Jackson (2017)
From eggs to hatchlings: nest site taphonomy of American crocodile (Crocodylus acutus) and broad-snouted caiman (Caiman latirostris).
PALAIOS 32(5): 337-348 
DOI: 10.2110/palo.2016.086 

Nesting behaviors of extant vertebrates can serve as taphonomic models for interpreting extinct archosaurian reproduction. Past studies have examined birds with open nests and nest-bound young and tortoises with buried nests and precocial young. Here we taphonomically describe nesting sites of two crocodylians, American crocodile (Crocodylus acutus) at Turkey Point, Florida and broad-snouted caiman (Caiman latirostris) from Santa Fe and Chaco provinces, Argentina. Surveys focused on eggshell abundance, orientation, and distribution and nest modification of successfully hatched nests. American crocodiles excavate triangular or semi-circular depressions into their nest during hatching. Maximum depths of these parent-assisted hatching traces ranged from 20–45 cm, with a breadth of 50–80 cm. Eggshell orientations outside these excavated pits favored concave down (53.1–80.0%). Broad-snouted caiman constructed mound nests of predominantly plant debris in forested areas with organic rich soil or on vegetation islands. Nests ranged in diameter from 1.2–1.6 m with a height of 0.3–0.6 m. Eggshell orientations within opened egg chambers favored concave up (61.8%), whereas fragments outside the chamber were nearly evenly distributed (51.8% concave-up). Eggshell distribution and orientation at these nesting sites result from adult females assisting and transporting eggs and young during hatching. Observed eggshell orientations in and around the egg chamber in caiman nests are similar to the 60:40 up:down hatching ratio reported in both bird and tortoise nests, whereas crocodile nests are more similar to a 40:60 ratio of trampled shell. Documentation of these nest characteristics and eggshell orientations may facilitate interpretations of parental assistance in the fossil record.


Abdelouahed Lagnaoui, Sebastian Voigt, Abouchouaib Belahmira, Hafid Saber, Hendrik Klein, Abdelkbir Hminna & Joerg W. Schneider (2017)
Late Carboniferous Tetrapod Footprints from the Souss Basin, Western High Atlas Mountains, Morocco.
Ichnos (advance online publication)
doi:  http://dx.doi.org/10.1080/10420940.2017.1320284   

The Late Carboniferous Souss Basin of south-central Morocco exhibits an approximately 1,800 m thick succession of fluvial and lacustrine deposits that have yielded diverse fossil remains of plants, insects, conchostracans, ostracods, jellyfish, fishes, and few tetrapod footprints. Recent exploration of ichnofossils of the Souss Basin led to the discovery of several trampled surfaces including tetrapod footprints assigned to the plexus Batrachichnus (Woodworth, 1900). Limnopus (Marsh, 1894), Dimetropus (Romer and Price, 1940), and Ichniotherium (Pohlig, 1892). These footprints can be referred to temnospondyl, basal synapsid (“pelycosaurian”), and diadectomorph trackmakers. The moderately diverse tetrapod footprint assemblage from the Souss Basin is important because it is the second-oldest record of tetrapod footprints from Africa and only the second record of the well-known ichnogenus Ichniotherium from outside of North America and Europe. Based on the variety of tetrapod tracks and previously collected floral and insect remains, the Souss Basin must have represented a well-established continental ecosystem during the Late Carboniferous.