Species Richness and Evidence of Random Patterns in Assemblages of South American Titanosauria during the Late Cretaceous (Campanian–Maastrichtian)

Abstract

The Titanosauria were much diversified during the Late Cretaceous, but paleobiological information concerning these sauropods continues to be scarce and no studies have been conducted utilizing modern methods of community analysis to infer possible structural patterns of extinct assemblages. The present study sought to estimate species richness and to investigate the existence of structures in assemblages of the South American Titanosauria during the Late Cretaceous. Estimates of species richness were made utilizing a nonparametric estimator and null models of species co-occurrences and overlapping body sizes were applied to determine the occurrence of structuring in this assemblages. The high estimate of species richness (n = 57) may have been influenced by ecological processes associated with extinction events of sauropod groups and with the structures of the habitats that provided abundant support to the maintenance of large numbers of species. The pseudocommunity analysis did not differ from that expected by chance, indicating the lack of structure in these assemblages. It is possible that these processes originated from phylogenetic inertia, associated with the occurrence of stabilized selection. Additionally, stochastic extinction events and historical factors may also have influenced the formation of the titanosaurian assemblages, in detriment to ecological factors during the Late Cretaceous. However, diagenetic and biostratinomic processes, influenced by the nature of the sedimentary paleoenvironment, could have rendered a random arrangement that would make assemblage structure undetectable.

How has our knowledge of dinosaur diversity through geologic time changed through research history?

“…The general patterns of ‘global’ subsampled diversity shows a steady increase from Middle to the end of Jurassic with a decline through J/K transition ( Upchurch & Mannion, 2012 ; Tennant, Mannion & Upchurch, 2016b ). The relatively high Late Cretaceous subsampled diversity levels can at least be partially explained by the constant discovery of new titanosaurian taxa, especially from Gondwanan continents ( Vieira et al, 2014 ; de Jesus Faria et al, 2015 ; Bandeira et al, 2016 ; Poropat et al, 2016 ), and only recently a more appreciated diversity of diplodocoids (e.g. dicraeosaurids, rebbachisaurids) from relatively poorly sampled regions such as Africa ( Mannion & Barrett, 2013 ; Wilson & Allain, 2015 ; Ibrahim et al, 2016 ).…”

How has our knowledge of dinosaur diversity through geologic time changed through research history?

“…The general patterns of 'global' subsampled diversity shows a steady increase from Middle to the end of Jurassic with a decline through J/K transition Tennant, Mannion & Upchurch, 2016b). The relatively high Late Cretaceous subsampled diversity levels can at least be partially explained by the constant discovery of new titanosaurian taxa, especially from Gondwanan continents (Vieira et al, 2014;de Jesus Faria et al, 2015;Bandeira et al, 2016;Poropat et al, 2016), and only recently a more appreciated diversity of diplodocoids (e.g. dicraeosaurids, rebbachisaurids) from relatively poorly sampled regions such as Africa (Mannion & Barrett, 2013;Wilson & Allain, 2015;Ibrahim et al, 2016).…”

What do giant titanosaur dinosaurs and modern Australasian megapodes have in common?

“…Titanosaurs populated every continent including Antarctica ( Curry Rogers, 2005 ; Mannion et al, 2011 ; Cerda et al, 2012 ) and according to Mannion & Upchurch (2010) and Mannion & Upchurch (2011) they preferred inland rather than coastal habitats. They experienced a great radiation during the Late Cretaceous, chiefly in South America, where more than 20 genera have been recorded ( Upchurch & Barrett, 2005 ; Zaher et al, 2011 ; Mannion et al, 2011 ; García et al, 2015 ; Vieira et al, 2014 ).…”