Brongniartella (trilobite)

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Brongniartella
Temporal range: Late Ordovician–Wenlock
Cephalon (1a) and pygidium (1b) of Brongniartella bisulcata.png
Cephalon (1a) and pygidium (1b) of Brongniartella bisulcata
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Arthropoda
Clade:† Artiopoda
Class:† Trilobita
Order:† Phacopida
Family:† Homalonotidae
Genus:† Brongniartella
Reed, 1918
Type species
Brongniartella bisulcata
M'Coy, 1851
Species

Brongniartella (sensu stricto)

  • B. bisulcata

"Brongniartella" group

  • at least 7 species, see text

Brongniartella is an extinct genus of homalonotid trilobite. It is of interest as it is a potential ancestor to the homalonotid trilobites Trimerus and Platycoryphe .

Contents

Description

Like other trilobites, Brongniartella is composed of three parts: a cephalon, a multisegmented thorax, and a pygidium. [1]

The cephalon is semicircular or semielliptical and lacks a border. The glabella is well-defined and urn-shaped or tapering forward, and generally lacks furrows. The axial furrows strongly converge in front of the occipital ring. The facial sutures are gonatoparian as they intersect the margin of the cephalon near the genal angles. The rostral suture is a wide curve on the upper side of the cephalon that is near or on the anterior margin. [1]

The 13-segmented thorax has a wide but indistinct axis, with extremely shallow axial furrows and the axis and pleurae being almost undistinguishable from the general concavity of the body. [2] [1] [3] The axial furrows of the thorax form a continuous depression, but each axial ring is also independently separated from the corresponding pleura by a shallow, transverse, oblique furrow corresponding to the one crossing the occipital ring from the base of the glabella. The base of each pleura between this transverse furrow and the pleural furrow is slightly swollen, and there is a peg-like interior projection on the posterior margin of each thoracic segment that fits into a corresponding notch of the succeeding thoracic segment. [3]

The pygidium is rounded and parabolic with a well-defined axis that ends in front of the posterior margin and a slightly indistinct, narrow posterior border. The pygidial ribs do not extend to the lateral margin of the pygidium. It is composed of 9-12 segments, and some forms bear a postaxial ridge.

Species and interrelationships

Brongniartella is traditionally considered to belong to the Eohomalonotinae, though some workers have assigned it to the Homalonotinae. [1] [4] Congreve and Lieberman 2008 performed a cladistic analysis of Ordovician homalonotids and found that Brongniartella was paraphyletic and the basal-most species of Homalonotinae, giving rise to the genera Trimerus and Platycoryphe . They proposed redefining the genus to only include the type species B. bisulcata and moving all other species to the paraphyletic "Brongniartella" group. [5]

Parsimony analysis of Congreve and Leiderman 2008: [5]

Brongniartella(sensu stricto) after Congreve and Lieberman, 2008 [5]

"Brongniartella" group [5]

References

  1. 1 2 3 4 Harrington, H. J. (1959-01-01). Treatise on Invertebrate Paleontology. Boulder (Colo.) Lawrence (Kan.): the Geological society of America & the University of Kansas press. ISBN   0-8137-3015-5.{{cite book}}: ISBN / Date incompatibility (help)
  2. 1 2 Whitcomb, L. (1930-06-30). "New Information on Homalonotus Trentonensis". Geological Society of America Bulletin. 41 (2): 341–350. Bibcode:1930GSAB...41..341W. doi:10.1130/GSAB-41-341. ISSN   0016-7606 . Retrieved 2025-10-28.
  3. 1 2 Reed, F. R. Cowper (1918). "IV.—Notes on the genus Homalonotus" (PDF). Geological Magazine. 5 (6): 263–276. Bibcode:1918GeoM....5..263R. doi: 10.1017/S0016756800194828 . ISSN   0016-7568 . Retrieved 2025-10-28.
  4. ↑ Thomas, A.T. (1977). "Classification and Phylogeny of Homalonotid Trilobites" (PDF). Palaeontology. 20: 159–178. Retrieved 2025-10-28.
  5. 1 2 3 4 Congreve, Curtis R; Lieberman, Bruce S (2008-09-10). "Phylogenetic and Biogeographic Analysis of Ordovician Homalonotid Trilobites" (PDF). The Open Paleontology Journal. 1 (1): 24–32. Bibcode:2008OPalJ...1...24C. doi: 10.2174/1874425700801010024 . ISSN   1874-4257 . Retrieved 2025-10-27.
  6. 1 2 3 Elicki, O. (2025-09-28). "New Ordovician fossils (bivalves, trilobites, brachiopods) from southern Jordan and re-evaluation of the regional Ordovician body fossil record". Bulletin of Geosciences 1933: 0. doi:10.3140/bull.geosci.1933. ISSN   1802-8225 . Retrieved 2025-10-28.
  7. 1 2 3 4 Dean, William Thornton (1961). "The Ordovician trilobite faunas of South Shropshire, II". Bulletin of the British Museum (Natural History) Geology. 5. doi:10.5281/ZENODO.16644797 . Retrieved 2025-10-27.
  8. ↑ Sandford, Andrew C. (2005). "Homalonotid trilobites from the Silurian and Lower Devonian of south-eastern Australia and New Zealand (Arthropoda: Trilobita: Homalonotidae)". Memoirs of Museum Victoria. 62 (1): 1–66. doi:10.24199/j.mmv.2005.62.1. ISSN   1447-2546 . Retrieved 2025-10-28.
  9. ↑ Henry, Jean-Louis (1996). "Classification de quelques Calymenina(Trilobita) ordoviciens: Calymenidae ou Homalonotidae?". Geobios. 29 (3): 331–340. Bibcode:1996Geobi..29..331H. doi:10.1016/S0016-6995(96)80034-9 . Retrieved 2025-10-28.
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