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The smallest known tetrapod footprints: Batrachichnus salamandroides from the Carboniferous of Joggins, Nova Scotia, Canada Matt Stimson1, Spencer G. Lucas2, and Gloria Melanson3 1. Saint Mary’s University, 923 Robie Street, Halifax, Nova Scotia B3H 3C3, Canada ¶ 2. New Mexico Museum of Natural History, 1801 Mountain Road N. W., Albuquerque, New Mexico 87104 USA ¶ 3. 70 Main Street, Joggins, Nova Scotia B0L 1AO, Canada A new trackway of Batrachichnus salamandroides from the classic Carboniferous section at Joggins, Nova Scotia, records the smallest example of tetrapod footprints known in the fossil record. The track maker was a juvenile, quadrupedal temnospondyl or microsaur with a trunk length of 3.55 mm and an estimated body length of 8 mm (skull, presacral vertebrae, and caudal vertebrae). The most conservative measurements, which include extramorphological features (i.e., toe drags), measure the manus and pes to have an average length and width of 1.58 mm × 1.65 mm and 2.38 mm × 2.54 mm, respectively. When the relative size of this trackway is compared with other previous described examples of Batachichnus salamandroides and other small vertebrate ichnotaxa from Joggins, it clearly is substantially smaller than previously described specimens. The 48-mm- long trackway preserves a high degree of extramorphological variation along its course, including a gait change associated with a change in direction, together with an increased stride and pace, and the appearance of overstepped imprints, in the latter part of the trackway. These morphological changes suggest the tetrapod changed from a walking gait to a running gait. Based on previous work, the case for a temnospondyl (branchiosaur, Eryops, or Dendrerpeton) track maker of Batrachichnus is strong. More than 100 fragmentary remains of Dendrerpeton have been prepared from the tree stumps recovered by Dawson in the late 19th century, and one articulated skeleton was collected and prepared from a siderite nodule. Previous work by Haubold compared skeletal reconstructions of the manus and pes anatomy of Dendrerpeton to that of Batrachichnus and made a compelling case for their similarity. Given the size
Copyright © Atlantic Geology 2012 AGS Abstracts - 38th Colloquium & Annual General Meeting 2012 Atlantic Geology, 2012, Volume 48, Number 1 Copyright © 2015 Atlantic Geology Atlantic Geology . Volume 48 . 2012 49
ranges of Limnopus and Batrachichnus at Joggins, and the known skeletal remains, Dendrerpeton (or some other, similar temnospondyl) is a strong candidate for the track maker of both ichnogenera at Joggins. Body proportion measurements, taken from the only known articulated temnospondyl represented at Joggins, an adult temnospondyl Dendrerpeton were used as a model to estimate the skull and body lengths of the track maker for the recently discovered Batrachichnus specimen.
Copyright © Atlantic Geology 2012 AGS Abstracts - 38th Colloquium & Annual General Meeting 2012