Ichnotaxonomic Review of Large Ornithopod Dinosaur Tracks: Temporal and Geographic Implications

Abstract

BackgroundLarge ornithopod tracks are known from the Upper Jurassic to the uppermost Cretaceous rocks of all continents but Antarctica. They include the tracks historically called Iguanodon footprints, iguanodontid footprints, hadrosaur/hadrosaurid footprints, and other large ornithopod tracks that have been used to define ichnotaxa. More than 40 ichnospecies based on large ornithopod tracks have been defined, but the validity of many of them is questionable.Methodology/Principal Findings34 ichnogenera and 44 ichnospecies have been analysed in this work. Many of them are considered to be invalid because they have been defined on the basis of poorly preserved tracks without diagnostic features, have an inadequate diagnosis, or are based on temporal and/or geographical criteria. Only eight ichnospecies belonging to the ichnogenera Caririchnium, Iguanodontipus and Hadrosauropodus are here regarded as valid.Conclusions/SignificanceThe monospecific ichnogenus Iguanodontipus (I. burreyi) is characterized by a small, rounded heel and elongate, narrow digit impressions. Its distribution is limited to the Berriasian-Valanginian of Europe. Caririchnium consists of four ichnospecies (C. magnificum [type ichnospecies], C. kortmeyeri, C. billsarjeanti and C. lotus) with a large, rounded heel and short, wide digit impressions. This ichnogenus ranges from the Berriasian-Hauterivian to the Aptian-Albian of South America, North America, Asia and Europe. Finally, Hadrosauropodus (three ichnospecies: H. langstoni [type ichnospecies], H. leonardii and H. kyoungsookimi) shows a large, bilobed heel and short, wide digit impressions. It is known from the Aptian-Albian to the Maastrichtian of North America, Asia and Europe. The ichnofamily Iguanodontipodidae includes large iguanodontian tracks characterized mainly by mesaxonic, tridactyl and subsymmetrical pes tracks that are as wide as (or wider than) long and have one pad impression in each digit and one in the heel. Its distribution is confidently limited to the Cretaceous of Europe, Asia, North America and South America.

The theropod that wasn't: an ornithopod tracksite from the Helvetiafjellet Formation (Lower Cretaceous) of Boltodden, Svalbard

“…Past v. 3.02 (Hammer et al 2001) was used for reduced major axis (RMA) regression, and for plotting and analysing compass directions. Use of size-class terminology follows Marty (2008) and Díaz-Martínez et al (2015).…”

“…It may represent a juvenile individual of the ichnotaxon described from Festningen (Hurum et al 2006) or indicate the presence of a new ornithopod taxon in the Barremian of Svalbard. Given that we currently have only a single well-preserved track and that it seems unlikely to have multiple coexisting species of medium-sized ornithopods in the Barremian of Svalbard, we refrain from naming a new taxon and, instead, refer this to Caririchnium sp., which is currently the only valid ornithopod ichnogenus recognized during this interval (Díaz-Martínez et al 2015).…”

“…Of large ornithopod ichnotaxa, eight Barremian and nine Aptian ichnogenera have been described worldwide (Díaz-Martínez et al 2015). In their recent review of large ornithopod dinosaur tracks, Díaz-Martínez et al (2015) only considered three genera valid. Iguanodontipus in the Berriasian -Valanginian, Caririchnium in the Berriasian -Albian and, finally, Hadrosauropodus in the Aptian-Maastrichtian.…”

“…From this review, it follows that all large ornithopod tracks from the Barremian are of the genus Caririchnium. Four ichnospecies of Caririchnium are known (Díaz-Martínez et al 2015): C. magnificum is found in Berrasian -Albianaged deposits of Brazil and Spain; C. kortmeyeri is only known from the Aptian -Albian of Canada; C. billsarjeanti is from the Aptian of Switzerland; and C. lotus is known from the Barremian-Albian of China and Spain (for a discussion, see Díaz-Martínez et al 2015). In the Aptian, only one Hadrosauropodus species is known, H. kyoungsookimi, which is found in Korea.…”

Síntesis Del Registro Fósil De Dinosaurios Tireóforos en Gondwana

“…Mientras Thulborn (1990) aceptó la interpretación original de Huene, Haubold (1971) sugirió que el productor pudo ser un ceratopsio. También en Brasil, icnitas de Caririchnium de la Formación Antenor Navarro (Berriasiense-Hauteriviense) de Paraíba fueron asig-nadas a un supuesto estegosaurio por Leonardi (1984Leonardi ( , 1989, pero han sido reinterpretadas como huellas producidas por un ornitópodo cuadrúpedo (Lockley y Wright, 2001;Díaz-Martínez et al, 2015).…”