page_title: Dvulikiaspis
section_title: Classification
hierarchical_section_title: Dvulikiaspis / Classification
caption_attribution_description: English: Hoplitaspis hiawathai, reconstruction. a Dorsal view. b Ventral view. The form of the first and second opercula are hypothetical and reconstructed based on comparison with Octoberaspis. Scale bar = 10 mm
context_page_description: Dvulikiaspis is a genus of chasmataspidid, a group of extinct aquatic arthropods. Fossils of the single and type species, D. menneri, have been discovered in deposits of the Early Devonian period in the Krasnoyarsk Krai, Siberia, Russia. The name of the genus is composed by the Russian word двуликий, meaning "two-faced", and the Ancient Greek word ἀσπίς, meaning "shield". The species name honors the discoverer of the holotype of Dvulikiaspis,
  Vladimir Vasilyevich Menner.
  Its prosoma was subquadrate to parabolic, with to subovate eyes and surrounded by a marginal rim. The abdomen was composed by a fused buckler and a postabdomen that occupied most of the body length. The appendages were uniform. The sixth and last pair of them had a paddle-like shape and was placed in front of the midpoint of the prosoma. The largest specimen was 2.64 centimetres long.
  The first fossil was described in 1959 as a new species of the eurypterid Stylonurus, while the other two were discovered in 1974. It would not be until 2014 when D. menneri was recognized as a chasmataspidid genus, being placed in the family Diploaspididae.
context_section_description: Dvulikiaspis is classified as part of the family Diploaspididae, one of the two families in the order Chasmataspidida. It includes one only species, D. menneri, from the Early Devonian of Siberia, Russia.
  D. menneri was originally recognized as a species of Stylonurus in 1959, being moved to Tylopterella in 1962 due to the apparent presence of paired tubercles in the tergites. Both conclusions, done by Novojilov, have been criticized. Lamsdell already commented the possibility that D. menneri could represent a chasmataspidid in 2011. This was demonstrated in 2014, when it was redescribed as a new genus of chasmataspidid and removed from Eurypterida, noting its distinction with other diploaspidids and suggesting a relationship with Loganamaraspis. In 2019, during the description of the new Ordovician chasmataspidid Hoplitaspis hiawathai, it was suggested that Dvulikiaspis, Hoplitaspis and Loganamaraspis could represent a new family separated from Diploaspididae. These genera share the proportionality of the body (the postabdomen comprises the majority of the body length), a poorly differentiated buckler and a paddle projecting in front of the midpoint of the prosoma, although this is not certain in Loganamaraspis. However, the creation of a new family was not considered correct at the moment and all three genera currently remain in Diploaspididae, which is considered pending a more extensive revision.
  The cladogram below is based on a larger study (simplified to only show chasmataspidids) from 2015 carried out by the paleontologists Paul A. Selden, Lamsdell and Liu Qi, expanded to include the species Diploaspis praecursor, described in 2017. It showcases the phylogenetic relationships within Chasmataspidida.
caption: Restoration of the related chasmataspidid Hoplitaspis hiawathai
exif: {}