Pulchratia Explained

Pulchratia is an extinct genus of brachiopods which lived in marine habitats during the Upper Carboniferous period. Its fossils have been found in North America.^{[1] [2] [3]}

Description

Like other echinoconchids, Pulchratia had recumbent spines arranged in irregular concentric bands, with the spines of this genus being mostly uniform in size and not having strong bases. It also has long lateral ridges which diverge from the hinge line. In these conditions it differs from the related Parajuresania, which has thicker posterior spines than anterior spines, and short cardinal ridges that parallel the hinge line, but otherwise the two genera are very similar. The buttress plates of Pulchratia are convergent, weak or entirely lost in adult specimens, while the lateral ridges are slightly divergent from the hinge.

Distribution

Fossil remains of Pulchratia are not known outside of North America, suggesting the genus may have been endemic to the continent. Remains of Pulchratia picuris have been found in the Watahomigi Formation of Arizona,^[4] and those of Pulchratia symmetrica are known from the Graham Formation of Texas and Mattoon Formation of Illinois.^{[5] [6]} Fossils from the Holder Formation of New Mexico have been assigned to Pulchratia aff. meeki.^[7] Specimens attributed to Pulchratia sp. have been collected from the Four Corners, Sausbee, and Takhandit formations of Kentucky, Oklahoma and Alaska respectively.^{[8] [9] [10]}

Classification

Muir-Wood & Cooper (1960) placed Pulchratia in the subfamily Echinoconchinae as they believed it lacked buttress plates. However Lazarev (1982) noted that the genus did indeed possess buttress plates as a juvenile at least, and transferred it into Juresaniinae.^[11] Leighton & Maples (2002) conducted multiple phylogenetic analyses which are strongly in agreement that the four subfamilies Buxtoniinae, Echinoconchinae, Pustulinae and Juresaniinae form the family Echinoconchidae, with Juresaniinae represented by Pulchratia and Parajuresania. The cladogram results of their phylogenetic analyses are displayed in the cladogram below:^[12]

Notes and References

1. Williams . Alwyn . Part H Brachiopoda (revised): Volumes 2 & 3, Linguliformea, Craniiformea, Rhynchonelliformea (part)., Treatise on Invertebrate Paleontology . Treatise on Invertebrate Paleontology . Geological Society of America . 2000 . 515 . 10.17161/dt.v0i0.5209 . en.
2. Muir-Wood . Helen . Cooper . G. Arthur . 1960 . Morphology, Classification and Life Habits of the Productoidea (Brachiopoda) . Geological Society of America Memoirs . 81 . 1–567 . 10.1130/MEM81-p1.
3. Dievert . Rylan V. . Gingras . Murray K. . Leighton . Lindsey R. . 2021-07-21 . The functional performance of productidine brachiopods in relation to environmental variables . Lethaia . en . 54 . 5 . 806–822 . 10.1111/let.12441 . 237713937 . 0024-1164.
4. The Supai Group of Grand Canyon . McKee . Edwin Dinwiddie . 1982 . U.S. Dept. of the Interior, Geological Survey ; For sale by the Supt. of Docs., U.S. G.P.O. . 1173 . 10.3133/pp1173 . en. free .
5. Austin . University of Texas at . 1938-01-01 . Stratigraphic and Paleontologic Studies of the Pennsylvanian and Permian Rocks in North-Central Texas . English . 10.15781/T28K75B9Z.
6. Scheihing . Mark H. . Langenheim . Ralph L. . 1980 . Brachiopods of the Suborder Strophomenidina from the Shumway Cyclothem, Mattoon Formation, Virgilian of Illinois . Journal of Paleontology . 54 . 5 . 1017–1034 . 1304367 . 0022-3360.
7. Kues . Barry S. . 2004 . Marine invertebrate assemblages from the Late Pennsylvanian (Virgilian) Holder Formation, Dry Canyon, Sacramento Mountains, south-central New Mexico . New Mexico Geology . en . 26 . 2 . 43–53 . 10.58799/NMG-v26n2.43 . 131175579 . 2837-6420.
8. Dennis . A.M. . Lawrence . D.R. . 1979 . Macrofauna and fossil preservation in the Magoffin marine zone, Pennsylvanian Breathitt Formation of eastern Kentucky USA . Southeastern Geology . 20 . 3 . 181–190.
9. Heim . Noel A. . 2009 . Stability of regional brachiopod diversity structure across the Mississippian/Pennsylvanian boundary . Paleobiology . en . 35 . 3 . 393–412 . 10.1666/0094-8373-35.3.393 . 2009Pbio...35..393H . 86535014 . 0094-8373.
10. Stratigraphy and paleontology of the revised type section for the Tahkandit Limestone (Permian) in east-central Alaska . Brabb . Earl E. . Grant . Richard E. . 1971 . U.S. Geological Survey . 703 . 10.3133/pp703 . en. free .
11. Lazarev . S.S. . 1982 . On some brachiopods of the family Buxtoniidae . Paleontological Journal. 16 . 1 . 65–73.
12. Leighton . Lindsey R. . Maples . Christopher G. . July 2002 . Evaluating internal versus external characters: Phylogenetic analyses of the Echinoconchidae, Buxtoniinae, and Juresaniinae (Phylum Brachiopoda) . Journal of Paleontology . en . 76 . 4 . 659 . 10.1666/0022-3360(2002)076<0659:EIVECP>2.0.CO;2 . 0022-3360.