An Italian dinosaur Lagerstätte reveals the tempo and mode of hadrosauriform body size evolution

Abstract

During the latest Cretaceous, the European Archipelago was characterized by highly fragmented landmasses hosting putative dwarfed, insular dinosaurs, claimed as fossil evidence of the “island rule”. The Villaggio del Pescatore quarry (north-eastern Italy) stands as the most informative locality within the palaeo-Mediterranean region and represents the first, multi-individual Konservat-Lagerstätte type dinosaur-bearing locality in Italy. The site is here critically re-evaluated as early Campanian in age, thus preceding the final fragmentation stages of the European Archipelago, including all other European localities preserving hypothesized dwarfed taxa. New skeletal remains allowed osteohistological analyses on the hadrosauroid Tethyshadros insularis indicating subadult features in the type specimen whereas a second, herein newly described, larger individual is likely somatically mature. A phylogenetic comparative framework places the body-size of T. insularis in range with other non-hadrosaurid Eurasian hadrosauroids, rejecting any significant evolutionary trend towards miniaturisation in this clade, confuting its ‘pygmy’ status, and providing unmatched data to infer environmentally-driven body-size trends in Mesozoic dinosaurs.

Relict duck-billed dinosaurs survived into the last age of the dinosaurs in subantarctic Chile

“…An isolated and incomplete tooth from the Maastrichtian of Vega Island in the Antarctic Peninsula was attributed to Hadrosauridae and tentatively to Hadrosaurinae (=Saurolophinae) because of its relatively symmetrical crown, with a single and nearly straight medial keel, and poorly developed denticles ( 13 ). Although teeth are unknown in most non-hadrosaurid duckbills, including Gonkoken , these characters are documented in forms transitional to Hadrosauridae as in the maxillary teeth of Eotrachodon ( 34 ) and also in earlier lineages, as in the dentary teeth of Tethyshadros ( 48 ) and the maxillary teeth of Eolambia ( 28 ). Also from the Antarctic Peninsula, a metatarsal fragment found in Maastrichtian rocks of Seymour Island was attributed to Hadrosauridae ( 12 ), but its morphology has already been pointed out to be shared by other ornithopods, including those that inhabited austral regions such as the Elasmaria ( 49 ) and, now, non-hadrosaurid duckbills.…”

“…Although the results of Biogeographic statistics did not support an Atlantogean route (from Europe via Africa) for the ancestors of Gonkoken , this could be a result of a sampling bias against latest Cretaceous faunas in Africa, which are poorly known ( 5 , 63 , 64 ). Non-hadrosaurid duckbills like Tethyshadros were present in Europe in the early Campanian ( 26 , 40 , 48 ), and later in the Maastrichtian, Lambeosaurine hadrosaurids managed to disperse from Europe into Africa despite the fact that these continents had drifted further apart ( 5 ). This has led to the suggestion that non-hadrosaurid duckbills could have well done the same before that, during the Cenomanian-Campanian ( 48 ).…”

“…Non-hadrosaurid duckbills like Tethyshadros were present in Europe in the early Campanian ( 26 , 40 , 48 ), and later in the Maastrichtian, Lambeosaurine hadrosaurids managed to disperse from Europe into Africa despite the fact that these continents had drifted further apart ( 5 ). This has led to the suggestion that non-hadrosaurid duckbills could have well done the same before that, during the Cenomanian-Campanian ( 48 ). To explore this possibility, we added a hypothetical African taxon of non-hadrosaurid duckbill to our BioGeoBEARS and s-DIVA analyses, placing it between Gonkoken and Eotrachodon , or as sister to Gonkoken .…”

Evolution of Hadrosaurs in the Campanian of Laramidia: New Information from the Skull Roof and Braincase

“…This section also describes some considered characters that are currently unscored and excluded from the present analysis for various reasons, so that they might be revisited in future continuation of this work (Figure 5.2). Chiarenza et al (2021) The maximum parsimony analysis was run using PAUP* version 4.0a169 for Macintosh (Swofford 2002). Commands and settings follow those of Ramírez Velasco (2022) to ensure comparability of results.…”

“…Tethyshadros was rescored from "0" to "1", following Chiarenza et al (2021). (Brink et al 2014: fig.…”