Anomoepus, Hitchcock, 1848
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publication ID |
https://doi.org/ 10.4202/app.00707.2019 |
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persistent identifier |
https://treatment.plazi.org/id/03DF87EE-FFC4-FFEF-FCCF-FEF8425DF959 |
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treatment provided by |
Felipe |
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scientific name |
Anomoepus |
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Anomoepus ? isp.
Figs. 4 View Fig , 5 View Fig .
Material. —SHN.(JJS).ICNO.18, 29, 34, 37, 56, 74, 103, 105C; from Serra do Bouro, Boavista do Bouro, Santa Rita, Foz Velha, Cambelas Sul, Praia da Corva; Alcobaça (Kimmeridgian–lower Tithonian) and Sobral (upper Kimmeridgian– lower Tithonian) formations (for details see SOM: table S1).
Description. —Minute to small-sized (pes length 9–15 cm) tridactyl tracks ( Figs. 4 View Fig , 5 View Fig and SOM: table S2), slightly longer than wide (pes length/width ratio 0.85–1.22) with medium mesaxony (AT ratio 0.36–0.61). The tracks are gracile and slightly asymmetrical. The metatarsophalangeal pad impression is subtriangular. One specimen (SHN.(JJS). ICNO.56) shows a constriction in the digits, suggesting possible phalangeal pads. Digit III is the longest, digit IV being slightly longer than II. The digits are considerably thin. The hypices are almost symmetrical. The distal end of the digit impressions is acuminated, showing tapered claw mark impressions in some specimens. The interdigital angle II–IV is medium to high (ranging from 68–102°); the interdigital angles II–III and III–IV are quite similar, with variations between the specimens. SHN.(JJS).ICNO.18 probably shows the evidence of a manus mark, being oval in morphology, but no digits can be recognized.
Remarks.—Anomoepus- like tracks have been known ever since the earliest days of dinosaur ichnology, thanks to the descriptions by Hitchcock (1848, 1863). The ichnofamily Anomoepodidae was defined by Lull (1904, 1953), and subsequently Gierliński (1991) emended the diagnosis. Anomoepus - like tracks are well known from Early Jurassic deposits all around the world ( Díaz-Martínez et al. 2017 and references therein). Nonetheless, there are different views about how many ichnospecies should be considered valid ( Olsen and Rainforth 2003; Lockley and Gierliński 2006). As suggested by Lockley et al. (2009), Anomoepus is hard to identify “unless both manus and pes tracks are found”, and in many cases hallux impressions may not be present when the trackmaker was progressing bipedally. The latter authors also pointed out the difficulties of distinguishing Anomoepu s-like tracks from other tridactyl or tetradactyl dinosaur footprints, and suggested that trackway configuration may help in drawing this distinction. However, the absence of complete trackways in the studied sample precludes the use of trackway configuration to resolve the issue. Although notably abundant in Early Jurassic deposits, Anomoepu s-like tracks are much scarcer in the context of younger deposits from the Late Jurassic. Lockley et al. (2009) suggested that “there is a significant gap in the distribution of Anomoepodidae between the early Jurassic and the early Cretaceous”. However, Anomoepus -like tracks have been described from the Late Jurassic of Asturias, Spain and the USA ( Foster and Lockley 2006; Lockley et al. 2008; Piñuela Suarez 2015) and subsequently at the beginning of the Cretaceous with Neoanomoepus ( Lockley et al. 2009) . The studied tracks differ considerably with respect to the diagnosis of Neoanomoepus in that the pes is tridactyl instead of tetradactyl. The relation of the studied tracks to the ichnofamily Anomoepodidae should be taken with caution as they do not comply with one of the main features of the diagnosis, namely “pedal digits II, III, and IV tend to be subequal in length”. Nonetheless, we consider that the studied tracks resemble the group of tracks classified as Anomoepus found in Late Jurassic deposits from several areas, and this is why we have classified them with open nomenclature (see also discussion). It should be highlighted that there are some differences in digit width among the specimens. Notably, SHN. (JJS).ICNO.56 ( Fig. 4B View Fig ) and SHN.(JJS).ICNO.18B ( Fig. 5D View Fig ) look more gracile, with lower digit widths. These might just be extramorphological differences, as seen in the differences in the values of morphological quality (M-Preservation; Marchetti et al. 2019).
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