Didactyl Tracks of Paravian Theropods (Maniraptora) from the ?Middle Jurassic of Africa

Abstract

BackgroundA new dinosaur tracksite from ?Middle Jurassic sediments of the Irhazer Group on the plains of Agadez (Rep. Niger, northwest Africa) revealed extraordinarily well preserved didactyl tracks of a digitigrade bipedal trackmaker. The distinct morphology of the pes imprints indicates a theropod trackmaker from a paravian maniraptoran closely related to birds.Methodology/Principal FindingsThe early age and the morphological traits of the tracks allow for description of the new ichnotaxon Paravipus didactyloides. A total of 120 tracks are assigned to 5 individual trackways. The ‘medium-sized’ tracks with an average footprint length of 27.5 cm and footprint width of 23.1 cm are deeply imprinted into the track bearing sandstone.Conclusions/SignificanceA comparison with other didactyl tracks gives new insights into the foot morphology of advanced maniraptoran theropods and contributes to knowledge of their evolutionary history. The new ichnotaxon takes an important position in the ichnological fossil record of Gondwana and the mid-Jurassic biota worldwide, because it is among the earliest known records of paravian maniraptorans and of didactyl theropod tracks from Africa.

A new Dromaeosauripus (Dinosauria: Theropoda) ichnospecies from the Lower Cretaceous Hekou Group, Gansu Province, China

“…While we recognize the subjec− tivity inherently involved in ichnotaxonomy (owing to the subtle relationships between behaviour, substrate composi− tion, preservation, and the resultant track), we err on the side of caution in assigning the Yanguoxia tracks to Dromaeo− saripus (based on the aforementioned shared traits) rather than attempting to synonymize the preexisting species of Dromaeosauripus but erect a new ichnospecies to accommo− date the observed differences between those ichnotaxa (see following discussion). The divarication angles (mean: 19°) between digits III-IV in D. yongjingensis are greater than in Dromaeopodus (~5°; Li et al 2007), Paravipus (5-15°; Mudroch et al 2010), Dro− maeosauripus hamanensis (5-10°; Kim et al 2008), Dro− maeosauripus jinjuensis (8-14°; Kim et al 2012), and the un− named Morocco didactyl tracks (16°; Ishigaki and Lockley 2010), but less than in Velociraptorichnus (21-28°; Zhen et al 1994;Xing et al 2009) and Menglongipus (41-44°). One of the most striking differences is the digital pad formula: the x−1−3−4−x digital pad formula of D. yongjingensis differenti− ates it from other Dromaeosauripus (formula x−1−4−4−x; Kim et al 2008Kim et al , 2012, Dromaeopodus (formula x−1−3−3−x; Li et al 2007), and Menglongipus (formula x−1−2−1−x; Xing et al 2009); Velociraptorichnus and Paravipus lack distinct digital pads.…”

“…After a hiatus of more than a decade, a mass of new dromaeopodid track discoveries in China closely followed one another, in− cluding unnamed, Early Cretaceous dromaeosaurid tracks from Yanguoxia, Yongjing County, Gansu Province , new specimens of Velociraptorichnus, the new ichnotaxon Dromaeopodus shandongensis from the Early Cretaceous of Junan, Shandong Province (Li et al 2007), and Menglongipus sinensis from the Jurassic-Cretaceous bound− ary of Chicheng, Hebei Province (Xing et al 2009). Reports outside China include unnamed ichnites from the earliest Cretaceous of Germany (Richter et al 2007), unnamed ichni− tes of dubious quality from the Early Cretaceous of Utah (Lockley et al 2004), Dromaeosauripus hamanensis and the recently−erected Dromaeosauripus jinjuensis from South Korea (Kim et al 2008(Kim et al , 2012, Paravipus didactyloides from the Middle Jurassic of Niger (Mudroch et al 2010), and un− named tracks from possibly the Early Jurassic of Morocco (Ishigaki and Lockley 2010). Dromaeosaurid tracks have also been confirmed from the Late Cretaceous of Utah (Cow− an et al 2010).…”

Vertebrate Ichnopathology: Pathologies Inferred from Dinosaur Tracks and Trackways from the Mesozoic

“…The digit II impression of Paravipes didactyloides is superficially somewhat similar in morphology to digit II impressions of dromaeosaur tracks as they are rounded or oval in shape ( fig. 5 in Mudrock et al, 2011; in press a). Clearly, reasonably well-preserved trackways provide the best chance to avoid misidentification of pathologies or evolutionary digit reductions or habitual digit retractions.…”

Diverse dinosaur ichnoassemblages from the Lower Cretaceous Dasheng Group in the Yishu fault zone, Shandong Province, China

“…Other didactyl tracks of uncertain affinity include Paravipus didactyloides from the Middle Jurassic of Niger (Mudroch et al, 2011), and a didactyl footprint from the Lower Jurassic of Morocco (Ishigaki and Lockley, 2010) that may be an extramorphological variant of a tridactyl track: see Lockley et al (2013) for review. Paravipus is no deinonychosaurian track (Lockley et al, 2013) and may be a swim track (Milner A.R.C.…”