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[dinosaur] Eocene avifauna from Geiseltal (German) + marine tetrapod fins + Triassic sauropterygian from Alpujarride

Ben Creisler

Some new non-dino papers:

Gerald Mayr (2020)
An updated review of the middle Eocene avifauna from the Geiseltal (Germany), with comments on the unusual taphonomy of some bird remains.
Geobios (advance online publication)
doi: Âhttps://doi.org/10.1016/j.geobios.2020.06.011

The brown coal mines of the Geiseltal were among the most important middle Eocene fossil localities and constitute the reference sites for the Geiseltalian stage of the European Land Mammal Mega Zones. Here, an updated review of the Geiseltal avifauna is given. Thirteen species are represented by diagnostic bones and can be referred to avian higher-level taxa, but various indeterminable albeit distinct fossils indicate a higher diversity of the Geiseltal avifauna. The majority of the Geiseltal fossils belong to taxa which are well known from early to mid-Ypresian fossil sites of Europe and North America. Some of the species from the Geiseltal are larger than their early Eocene relatives, but it remains elusive whether this indicates an evolutionary size increase in some avian lineages or reflects different palaeohabitats of the involved fossil sites. The Geiseltal avifauna exhibits some taphonomic peculiarities that have not yet been addressed. Most bird fossils consist of isolated bones or partial skeletons and here it is hypothesized that at least some of the fragmentary specimens represent feeding remains of crocodilians. For the first time, medullary bone, which is indicative of breeding females, is reported for birds from the Geiseltal. The comparative abundance of the coliiform species Eoglaucidium pallas is remarkable, and either this species was extremely abundant in the Geiseltal ecosystem or it had ecological preferences which favored its preservation.


Free pdf:

Marta S. FernÃndez, Evangelos Vlachos, MÃnica R. Buono, Lucia Alzugaray, Lisandro Campos, Juliana Sterli, Yanina Herrera and Florencia Paolucci (2020)
Fingers zipped up or baby mittens? Two main tetrapod strategies to return to the sea.
Biology Letters 16(8): Â20200281
doi: https://doi.org/10.1098/rsbl.2020.0281

Free pdf:

The application of network methodology in anatomical structures offers new insights on the connectivity pattern of skull bones, skeletal elements and their muscles. Anatomical networks helped to improve our understanding of the water-to-land transition and how the pectoral fins were transformed into limbs via their modular disintegration. Here, we apply the same methodology to tetrapods secondarily adapted to the marine environment. We find that these animals achieved their return to the sea with four types of morphological changes, which can be grouped into two different main strategies. In all marine mammals and the majority of the reptiles, the fin is formed by the persistence of superficial and interdigital connective tissues, like a 'baby mitten', whereas the underlying connectivity pattern of the bones does not influence the formation of the forefin. On the contrary, ichthyosaurs 'zipped up' their fingers and transformed their digits into carpal-like elements, forming a homogeneous and better-integrated forefin. These strategies led these vertebrates into three different macroevolutionary paths exploring the possible spectrum of morphological adaptations.

Free pdf:

M. Reolid &Â J. Reolid (2020)
First record of Triassic marine reptiles (Nothosauria, Sauropterygia) from the Alpujarride Complex (Internal Zones of the Betic Cordillera, Spain).Â
[Primer registro de reptiles marinos triÃsicos (notosaurios, sauropterigios) del Complejo AlpujÃrride (Zonas Internas de la Cordillera BÃtica, EspaÃa)]ÂÂ
Estudios GeolÃgicosÂ76(1): e126
doi: https://doi.org/10.3989/egeol.43592.535

Free pdf:

This work reports the first record in the Internal Zones of the Betic Cordillera of a vertebrate fossil remain, more exactly a rib, corresponding to a marine reptile (Sauropterygia). The development of epicontinental platforms restricted to the Tethys Ocean during the fragmentation of Pangea since the late Lower Triassic favoured the radiation of Sauropterygia, diapsid marine reptiles including Placodontiformes, Pachypleurosauria, Nothosauroidea, and Pistosauroidea. The Triassic of the Alpujarride Complex, in the Internal Zones of the Betic Cordillera, SE Spain, comprises the carbonate deposits of these epicontinental platforms developed during the Middle-Late Triassic in the northern margin of the Mesomediterranean Massif. The studied stratigraphic interval is located at Sierra de LÃjar (Granada Province) and consists of 17.5-m thick succession of alternating fossiliferous marls and limestones with local intense bioturbation and abundance of macroinvertebrates. The studied interval represents shallow facies of the inter- to subtidal environment as deduced by the record of Lofer cycles and the record of carbonated breccia at the top of the sequence likely related to storm events. Lofer cycles display lamination at their bases and intense bioturbation and abundant bivalves towards the top. A 15-cm long dorsal rib of a sauropterygian, likely a nothosaur, was recorded in this succession. It is well preserved, without evidence of original fragmentation, borings, or encrustations. This study shows for the first time fossil bones of marine reptiles in the Alpujarride Complex, which inhabited the shallow-water environments during the Triassic, equivalent to the marine reptiles recorded in other areas such as the Iberian Palaeomargin and other central Europe basins.


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