Cigara

Cigara Temporal range: Middle Cambrian PreꞒ Ꞓ O S D C P T J K Pg N
Scientific classification
Kingdom:	Animalia
Phylum:	Echinodermata
Class:	† Eocrinoidea (?)
Genus:	† Cigara Barrande 1887
Type species
†C. dusli
Species
C. dusliBarrande 1887

Cigara ^[1] (sometimes misspelled Cigaria) ^[2] is an extinct echinoderm genus of uncertain affinities, generally placed incertae sedis within the Eocrinoidea. ^{[3] [4]} It contains a single species, C. dusli, that is known only from two incomplete specimens on a single slab collected from the Middle Cambrian Jince Formation of the Czech Republic. ^[2]

Description

The body of Cigara has three parts, with the middle part creating a roughly 40° bend between the conical outer parts. The middle part features an unusual lattice structure of thin elongate plates crossing in X-shaped patterns. Neither of the specimens preserve the end of either cone, and no feeding appendages are apparent. ^[2]

Classification

The assignment of Cigara to the Eocrinoidea has been based on the presence of respiratory structures known as epispires in middle section of the body. ^[2] Respiratory structures have traditionally been used to assign blastozoan echinoderms to traditional classes. However, this is no longer seen as a way to define monophyletic clades due to the diversity of structures, as well as convergent evolution of similar structures in different groups. ^[5]

While Cigara was initially grouped with other eocrinoid genre, the 1967 Treatise on Invertebrate Paleontology deemed these associations "unacceptable" and placed it in the section for unclassified eocrinoids. ^[3]

In his 1973 classification that established Blastozoa (including Eocrinoidea) as a subphylum, James Sprinkle noted that epispires appear in other classes of early echinoderms, including Stylophora. He further noted that the only structures similar to the X-shaped lattice appear in stylophorans, and that Cigara could be a "very early and perhaps abberrant" stylophoran. Based on this, Sprinkle predicted that when complete specimens are found, they will not have the biserial brachioles characteristic of blastozoans. However, while he advocated removing Cigara from Eocrinoidea, Sprinkle did not assign it to Stylophora. He considered that Cigara might warrant being placed in its own class, but that there was not enough clear information to formally erect such a class. ^[2]

Later taxonomies have continued to include Cigara in Eocrinoidea, albeit tentatively. ^[4]

References

1. "IRMNG - Cigara Barrande, 1887 †". Interim Register of Marine and Nonmarine Genre.
2. Sprinkle, James (1973). "Morphology and evolution of blastozoan echinoderms". Special Publication of the Museum of Comparative Zoology, Harvard University. Retrieved 29 October 2024.
3. Ubaghs, Georges (1967). "Eocrionidea". In Moore, Raymond C. (ed.). Treatise on Invertebrate Paleontology, Part S: Echinodermata 1. Vol. 1. University of Kansas Press. pp. S455 –S495. Retrieved 29 October 2024.
4. Sepkowski, J. John (16 September 2002). "A compendium of fossil marine animal genera". Bulletins of American Paleontology (363).
5. Sheffield, Sarah L.; Limbeck, Maggie R.; Bauer, Jennifer E.; Hill, Stephen A.; Nohejlová, Martina (2022). Sumrall, Colin D. (ed.). A Review of Blastozoan Echinoderm Respiratory Structures. Elements of Paleontology. Cambridge: Cambridge University Press. doi:10.1017/9781108881821. ISBN   9781108794725.