Titanoprosoma
| Titanoprosoma Temporal range: | |
|---|---|
 | |
| Diagrammatic reconstruction of T. edgecombei | |
Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Subphylum: | Chelicerata |
| Clade: | Euchelicerata |
| Class: | incertae sedis |
| Genus: | †Titanoprosoma Bicknell, Kimmig, Smith & Scherer, 2024 |
| Species: | †T. edgecombei |
| Binomial name | |
| †Titanoprosoma edgecombei Bicknell, Kimmig, Smith & Scherer, 2024 | |
Titanoprosoma is an extinct genus of chelicerate with uncertain affinities. The only known species is T. edgecombei, found in the Serpukhovian Bear Gulch Limestone in Montana.[1]
Discovery and naming
T. edgecombei is only known from its holotype. This specimen was discovered in the Bear Gulch Limestone in Fergus County, Montana and dates back to the Serpukhovian stage of the Carboniferous. It was collected by commercial collectors and sold in 1995 to the State Museum of Natural History Karlsruhe, Germany.[1] The Bear Gulch Limestone is a Plattenkalk Konservat Lagerstätte.[2] Depending on the study, it is considered a member of the Heath Formation or the Tyler Formation.[1][3][4]
The generic name reflects the particularly large size (titan) of the head shield (prosoma). The specific name honors Gregory Edgecombe, a paleontologist specialized in arthropods.[1]
Description
The total body length of the holotype is 38.1 mm. The prosoma is completely preserved. It is 22 mm long and 17.5 mm wide. It is ovate and the dorsal side appears to be entirely structureless (including the lack of dorsal eyes); this is called an effaced prosoma. A prosoma of such size and shape was unknown prior to the discovery of T. edgecombei. The opisthosoma is 8.4 mm long and is composed of seven tergites. The anteriormost is 11.6 mm wide. The next one is much narrower at 6.7 mm. From this tergite, the width tapers smoothly toward the posteriormost one. The telson is 8.4 mm long.[1]
Affinities
The very large size of the prosoma combined with its ovate shape makes T. edgecombei unique among chelicerates.[1] Some examples of fossil chelicerates with ovate to round prosoma include Alanops and Prolimulus.[5][6] Titanoprosoma is distinct from eurypterids because of the lack of a metasoma. It superficially looks like horseshoe crabs; however, it lacks their typical thoracetron (fused opisthosoma). Chasmataspidids are also excluded because of the lack of buckler-like shape along the opisthoma and the lack of nine postabdominal segments. Titanoprosoma also looks like some synziphosurines, however, it lacks a pretelson and has fewer tergites. Synziphosurines are not known to possess such an ovate prosoma. This shape differentiates Titanoprosoma from the co-occurring chelicerate Anderella. Another possibility is that Titanoprosoma belongs to Aglaspidida.[1] Brachyaglaspis possesses a large head region and few trunk tergites;[7] however, Titanoprosoma does not preserve any evidence of the typical postventral plates. Thus, Titanoprosoma is tentatively assigned to Euchelicerata.[1]
References
- 1 2 3 4 5 6 7 8 Bicknell, Russell D.C.; Kimmig, Julien; Smith, Patrick M.; Scherer, Torsten (2024-02-01). "An Enigmatic Euchelicerate from the Mississippian (Serpukhovian) and Insights into Invertebrate Preservation in the Bear Gulch Limestone, Montana". American Museum Novitates (4008). doi:10.1206/4008.1. ISSN 0003-0082.
- ↑ Hagadorn, J.W. (2002). "Bear Gulch: an exceptional upper Carboniferous plattenkalk". Exceptional Fossil Preservation: A Unique View on the Evolution of Marine Life: 167–183.
- ↑ Cox, Robt S. (July 1986). "Preliminary report on the age and palynology of the Bear Gulch Limestone (Mississippian, Montana)". Journal of Paleontology. 60 (4): 952–956. Bibcode:1986JPal...60..952C. doi:10.1017/S0022336000043092. ISSN 0022-3360.
- ↑ Singer, A. E. (2021). Benthic Invertebrate Paleontology of the Late Mississippian (Serpukhovian) Bear Gulch Limestone, Central Montana. University of Montana.
- ↑ Racheboeuf, Patrick R.; Vannier, Jean; Anderson, Lyall I. (January 2002). "A New Three-Dimensionally Preserved Xiphosuran Chelicerate from the Montceau-Les-Mines Lagerstätte (Carboniferous, France)". Palaeontology. 45 (1): 125–147. Bibcode:2002Palgy..45..125R. doi:10.1111/1475-4983.00230. ISSN 0031-0239.
- ↑ Lustri, Lorenzo; Laibl, Lukáš; Bicknell, Russell D. C. (2021-03-08). "A revision of Prolimulus woodwardi Fritsch, 1899 with comparison to other highly paedomorphic belinurids". PeerJ. 9 e10980. doi:10.7717/peerj.10980. ISSN 2167-8359. PMC 7950201. PMID 33732551.
- ↑ Ortega-Hernández, Javier; Roy, Peter Van; Lerosey-Aubril, Rudy (2016). "A new aglaspidid euarthropod with a six-segmented trunk from the Lower Ordovician Fezouata Konservat-Lagerstätte, Morocco". Geological Magazine. 153 (3): 524–536. Bibcode:2016GeoM..153..524O. doi:10.1017/S0016756815000710. hdl:1854/LU-8714213. ISSN 0016-7568.