ABSTRACT

A new hard-shelled sea turtle (Pan-Cheloniidae) with vestigial soft tissues from the lower Eocene (Ypresian) Fur Formation of Denmark is described and illustrated. The fossil (DK 807) comprises a partial, yet fully articulated carapace (estimated original length ∼50 cm) where the individual bones mostly are preserved in three dimensions, together with an intact sacrum, a consecutive series of articulated caudal vertebrae, a complete pelvic girdle, and both hind limbs. Primitive characters in the pelvis and limbs, along with free ribs that contact the posterior peripherals suggest affinity with the extinct pan-cheloniid Eochelone; however, because of the incomplete nature of the fossil, DK 807 is kept in open nomenclature. Associated with the skeletal elements are soft-tissue residues that include remnant epidermal scutes and a nearly complete outline of a rear paddle. The flipper-shaped halo likely represents traces of skin preserved as a dark bedding-parallel film. Its wrinkled and striated surface texture attests to an originally scaleless configuration comparable to the soft integument of living adult dermochelyid (leatherback) turtles, and unlike that of extant cheloniids. Scratches, scars and indentations on the bony carapace likely represent incompletely healed bite marks inflicted by a crocodylian or another large-sized seagoing tetrapod.

摘要

描述和说明了一种新的硬壳海龟（Pan-Cheloniidae），其软组织来自丹麦的始新世（伊普勒西亚）下层毛皮地层。化石 (DK 807) 包括一个部分但完全铰接的甲壳（估计原始长度约 50 厘米），其中单个骨骼大部分保存在三个维度上，连同完整的骶骨、一系列连续的铰接尾椎、完整的骨盆腰带，和两个后肢。骨盆和四肢的原始特征，以及与后周边接触的游离肋骨表明与已灭绝的泛龟类Eochelone 有亲缘关系; 然而，由于化石的不完整性质，DK 807 保持开放命名。与骨骼元素相关的是软组织残留物，包括残余的表皮盾片和几乎完整的后桨轮廓。鳍状的光环可能代表作为深色床上用品平行薄膜保存的皮肤痕迹。它的皱纹和条纹表面纹理证明了原始无鳞的构造可与活的成年皮甲龟（皮背龟）的柔软外皮相媲美，而不像现存的龟类。骨甲壳上的划痕、疤痕和凹痕可能代表鳄鱼或其他大型海上四足动物造成的未完全愈合的咬痕。