The Hawkesbury Sandstone (Hawkesbury Series, Sydney Basin) on the southeastern coast of New South Wales, Australia, preserves a depauperate but important vertebrate tetrapod body-fossil record from the Early and Middle Triassic. As with many fossil sites around the world, the ichnological record has helped to shed light on the paleoecology of this interval. Herein, we investigate historical reports of a trackway pertaining to a putative short-tailed reptile found at Berowra Creek in the 1940s. Reinvestigation of the surviving track-bearing slabs augmented by archival photographs of the complete trackway, suggests that these impressions, which consist primarily of didactyl tracks (plus less common monodactyl and tridactyl traces), represent the earliest example of a swimming tetrapod found in Australia. Another isolated specimen (possibly from a nearby locality at Annangrove) appears to represent similar didactyl swim traces of a second, larger individual. Although the identities of the trackmakers are unknown, the Berowra Creek individual had an estimated body length of between ~80 cm (short-coupled) and 1.35 m (long-coupled), and produced the subaqueous trackway while travelling upslope (against the current) on a sandbar within a braided river system of the Hawkesbury Sandstone. These trackways partially resemble amphibian swim traces in the so-called Batrachichnus C Lunichnium continuum, but appear to represent a unique locomotion trace. This reanalysis of the Berowra Creek trackway provides insight into the locomotion of tetrapods of the Triassic Hawkesbury Series, which remains a poorly understood aspect of their life history.

中文翻译：

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澳大利亚最早的四足动物游泳痕迹来自悉尼盆地的霍克斯伯里砂岩（中三叠纪）

位于澳大利亚新南威尔士州东南海岸的霍克斯伯里砂岩（霍克斯伯里系列，悉尼盆地）保存了早三叠世和中三叠世的一个荒废但重要的脊椎动物四足动物身体化石记录。与世界各地的许多化石遗址一样，化石记录有助于阐明这一时期的古生态学。在此，我们调查了有关 1940 年代在 Berowra Creek 发现的假定短尾爬行动物的轨道的历史报告。通过完整轨道的档案照片对幸存的履带承载板进行重新调查，表明这些印象主要由指示迹（加上不太常见的单趾和三趾迹）组成，代表了在澳大利亚发现的游泳四足动物的最早例子。另一个孤立的标本（可能来自附近的安南格罗夫地区）似乎代表了第二个更大个体的类似教化游泳痕迹。虽然轨道制造者的身份未知，但 Berowra Creek 个体的估计体长在约 80 cm（短耦合）和 1.35 m（长耦合）之间，并在上坡行驶（逆流）时形成了水下轨道在霍克斯伯里砂岩的辫状河流系统内的沙洲上。这些轨道部分类似于所谓的两栖动物游泳痕迹 并在霍克斯伯里砂岩的辫状河流系统内的沙洲上（逆流）上行时产生了水下轨道。这些轨道部分类似于所谓的两栖动物游泳痕迹 并在霍克斯伯里砂岩的辫状河流系统内的沙洲上（逆流）上行时产生了水下轨道。这些轨道部分类似于所谓的两栖动物游泳痕迹鲶鱼C鎏金连续体，但似乎代表了一个独特的运动轨迹。对 Berowra Creek 轨道的重新分析提供了对三叠纪霍克斯伯里系列四足动物运动的深入了解，这仍然是他们生活史中一个鲜为人知的方面。