Asterodermidae

Asterodermidae (also referred to as Spathobatidae) is an extinct family of rays known from the Late Jurassic epoch. Asterodermidae is the only family within the order Apolithabatiformes (spinorays). All named genera within this family are known from Europe, although a specimen from Argentina may also have affinities with these taxa. The general body plan of asterodermids is reminiscent of modern guitarfish.^[2]

Well-preserved holomorphic ray fossils have been known from Late Jurassic Lagerstätte deposits throughout Europe since the mid-19th century, characterized by their complete, articulated preservation including soft tissue outlines. Asterodermus,^[3] Spathobatis,^[4] and Belemnobatis^[5] were named in 1836, 1849, and 1852, respectively. In 1850, Charles Lucien Bonaparte first mentioned the clade Asterodermini (with Asterodermus as the type genus).^[6] As such, the family-level name Asterodermidae is also attributed to Bonaparte.^[1] An 1888 publication by Wilhelm Dames is the first known mention of the family Spathobatidae, albeit without a formal diagnosis or description.^[7] While this would not be accepted by the modern guidelines of the International Code of Zoological Nomenclature, the establishment of the name before 1999 allows for its use. This publication went largely unnoticed until 2024,^[8] so researchers in the early 21st century falsely attributed the clade's authorship to Underwood, 2006.^[9][10][11]

Kimmerobatis, an additional genus, was described in 2019.^[10] A thorough review of Jurassic batomorphs in 2024 allowed researchers to reidentify several specimens previously categorized as a large Spathobatis morphotype as belonging to the new genus Aellopobatis.^[8] Apolithabatis was named based on a single well-preserved specimen the following year, with the order Apolithabatiformes erected with this as the type genus.^[2] The common name "spinorays" was proposed for apolithibatiforms, referencing their unique dorsal fin spines. The name is also an allusion to "rhinorays", the common name of rhinopristiforms, which is the clade asterodermids were originally assigned to.^[1]

While the family name Spathobatidae was used in reference to these taxa for several years,^[8][2] a 2025 nomenclatural comment noted the priority of the name Asterodermidae, indicating it should be used instead.^[1]

The phylogenetic relationships of these Jurassic batomorphs have been unclear. Some researchers have expressed uncertainty regarding whether "spathobatids" ("asterodermids") form a paraphyletic or monophyletic group and to which order they belong.^[10][8]

In their 2025 description of Apolithabatis, Türtscher et al. analyzed most of the Jurassic European holomorphic ray fossils. Their phylogenetic analysis placed all of these taxa in a monophyletic clade at the base of Batomorphi, outside of the crown group (all of the extant rays and their closest relatives). As such, they established the new order Apolithabatiformes to hold the family Spathobatidae (Asterodermidae). The authors emphasized that, while several consistent characters unite these genera within a group, the order is a working hypothesis subject to change with the future description of additional specimens. Their results are displayed in the cladogram below:^[2]

• Paleobiota of the Solnhofen Limestone