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| Sauripes hadongensis Lee, Lee, Fiorillo & Lü, 2018 A reconstruction of a lizard running bipedally chased by the pterosaur Pteraichnus koreanensis, based on the trackway.
Illustration: Chuang Zhao
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Abstract
Four heteropod lizard trackways discovered in the Hasandong Formation (Aptian-early Albian), South Korea assigned to Sauripes hadongensis, n. ichnogen., n. ichnosp., which represents the oldest lizard tracks in the world. Most tracks are pes tracks (N = 25) that are very small, average 22.29 mm long and 12.46 mm wide. The pes tracks show “typical” lizard morphology as having curved digit imprints that progressively increase in length from digits I to IV, a smaller digit V that is separated from the other digits by a large interdigital angle. The manus track is 19.18 mm long and 19.23 mm wide, and shows a different morphology from the pes. The predominant pes tracks, the long stride length of pes, narrow trackway width, digitigrade manus and pes prints, and anteriorly oriented long axis of the fourth pedal digit indicate that these trackways were made by lizards running bipedally, suggesting that bipedality was possible early in lizard evolution.
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| Figure 1 Photograph and drawing of lizard trackways on the block. |
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| Figure 5 A reconstruction of a lizard running bipedally chased by the pterosaur Pteraichnus koreanensis, based on the trackway (Drawn by Chuang Zhao). |
Systematic ichnology
Order Squamata Oppel, 1811
Sauripes hadongensis ichnogen. et ichnosp. nov.
Etymology: Ichnogenus named from ancient Greek “sauros” (lizard) and “pes” (foot). Ichnospecies named after Hadong County that yielded the holotype.
Holotype: Manus and pes prints on a mudstone slab (70 × 30 cm) (KIGAM VP 201501: Korea Institute of Geoscience and Mineral Resources, Vertebrate Paleontology).
Type locality and horizon: Hasandong Formation, Lower Cretaceous (Aptian-early Albian), an abandoned quarry next to Hadong power plant, Hadong County, South Gyeongsang Province, South Korea.
Diagnosis: Quadrupedal tracks; manus prints are medial to the pes prints; the pes prints are larger than the manus prints; plantigrade and pentadactyl pes prints are longer than wide; the digit length progressively increasing from digits I to IV (ectaxonic); digit V is oriented more laterally and offset from other digits; digit imprint IV is more than twice the length of the metatarsal impression; plantigrade and pentadactyl manus print has similar length and width dimensions; digits II and IV are shorter than digit III (mesaxonic); the interdigital angle between digits I and V of the manus is larger than that of the pes.
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| Figure 2 Manus and pes tracks of Sauripes hadongensis, n. ichnogen., n. ichnosp. (a) Enlarged photograph and drawing of a manus imprint (B1). (b) A pes imprint (A6). Scale bars equal 1 cm. |
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| Figure 3 Pes tracks of Sauripes hadongensis, n. ichnogen., n. ichnosp. (a) Enlarged photograph and drawing of a pes imprint (A3). (b) A pes imprint (B8). (c) A pes imprint (B9). Scale bars equal 1 cm. |
Hang-Jae Lee, Yuong-Nam Lee, Anthony R. Fiorillo and Junchang Lü. 2018. Lizards ran Bipedally 110 Million Years Ago. Scientific Reports. 8, Article number: 2617. DOI: 10.1038/s41598-018-20809-z
Fossil Footprints Are Oldest Traces of Lizards Running on Two Legs on.natgeo.com/2F5CSKK via @NatGeo
