Xenechinus parvus Kier, 1958
Plate: XePa-10
Series: Permian Group: Formation: Wolfcamp
Locale: Hess Canyon County: Brewster Stage: Wolfcampian
Length: 5.1 mm (Holotype)
Specimens in photos: U.S.N.M. 136486, 136487, 136488, 136505 Holotype and Paratypes.
Paleobiology Depart. NMNH, Smithsonian Institution
Collector: USGS/Cooper
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 136486 (Kier, 1958).
Locality: USNM Locality 706x, Hess Canyon, Glass Mountains, Brewster County, Texas.
Stratigraphy: Wolfcamp Formation (Upper Part).
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Perischoechinoidea M'Coy, 1849
Order: Palaechinoida Haeckel, 1896
Family: Palaechinidae M'Coy, 1849
Genus: XENECHINUS Kier, 1958
Species: Xenechinus parvus Kier, 1958
TYPE SPECIES: Xenechinus parvus Kier, 1958
DIAGNOSIS
A very small, subspherical palaechinoid. Ambulacra are composed of two columns of primary plates and two columns of demiplates, creating four columns of pores. Interambulacra are composed of three columns of plates at the ambitus (Kier, 1958).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Wolfcampian Series
Formations: Wolfcamp Formation.
Stratigraphic Units: Permian, Cisuralian (Wolfcampian).
Counties: Brewster.
Abundance: Rare; known from the type series.
DESCRIPTION
TOP: Length: 5.1 mm (Holotype). Top shape: Subspherical (Kier, 1958).
SIDE: Side shape: Rounded sides.
AMB: Amb shape: Wide; wider than interambulacra at the ambitus. Amb arrangement: Composed of 4 columns of plates (two primary, two demiplates). Pore zones are wide.
PORE PAIRS: Arrangement: Four vertical rows of pore pairs. Pores are round, slightly elongated, and slightly oblique. Tubercles are present between sets of pore pairs. Plating: The plating pattern is repetitive; demiplates are characteristic of the genus (Kier, 1958).
TUBERCLES: Primary Perforated: No (Imperforate). Distribution: Small secondary tubercles are scattered over the surface. Tubercles in interambulacra are about equal in size to those in the ambulacra.
GRANULES: See Tubercles.
FASCIOLE: Absent.
INTERAMB: Width: Narrower than ambulacra at the ambitus. Arrangement: Composed of 3 columns of hexagonal plates (Kier, 1958).
APICAL SYSTEM: Condition: Missing in all specimens (Kier, 1958).
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Condition: Missing. Lantern: Inclined auricles present (Kier, 1958).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
ETYMOLOGY
From the Latin parvus (small), referring to the diminutive size of the test.
REMARKS & COMPARISONS
Remarks: Kier (1958) established the genus Xenechinus for this species, noting its similarity to Melonechinus but distinguishing it by having only 3 columns of interambulacral plates (vs. 4 or more in Melonechinus) and 4 columns of ambulacral plates (vs. many in Melonechinus). It is one of the few Permian echinoids known from North America.
Comparisons:
Plate: XePa-10
Series: Permian Group: Formation: Wolfcamp
Locale: Hess Canyon County: Brewster Stage: Wolfcampian
Length: 5.1 mm (Holotype)
Specimens in photos: U.S.N.M. 136486, 136487, 136488, 136505 Holotype and Paratypes.
Paleobiology Depart. NMNH, Smithsonian Institution
Collector: USGS/Cooper
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 136486 (Kier, 1958).
Locality: USNM Locality 706x, Hess Canyon, Glass Mountains, Brewster County, Texas.
Stratigraphy: Wolfcamp Formation (Upper Part).
SYNONYMY
- Xenechinus parvus Kier, 1958
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Perischoechinoidea M'Coy, 1849
Order: Palaechinoida Haeckel, 1896
Family: Palaechinidae M'Coy, 1849
Genus: XENECHINUS Kier, 1958
Species: Xenechinus parvus Kier, 1958
TYPE SPECIES: Xenechinus parvus Kier, 1958
DIAGNOSIS
A very small, subspherical palaechinoid. Ambulacra are composed of two columns of primary plates and two columns of demiplates, creating four columns of pores. Interambulacra are composed of three columns of plates at the ambitus (Kier, 1958).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Wolfcampian Series
Formations: Wolfcamp Formation.
Stratigraphic Units: Permian, Cisuralian (Wolfcampian).
Counties: Brewster.
Abundance: Rare; known from the type series.
DESCRIPTION
TOP: Length: 5.1 mm (Holotype). Top shape: Subspherical (Kier, 1958).
SIDE: Side shape: Rounded sides.
AMB: Amb shape: Wide; wider than interambulacra at the ambitus. Amb arrangement: Composed of 4 columns of plates (two primary, two demiplates). Pore zones are wide.
PORE PAIRS: Arrangement: Four vertical rows of pore pairs. Pores are round, slightly elongated, and slightly oblique. Tubercles are present between sets of pore pairs. Plating: The plating pattern is repetitive; demiplates are characteristic of the genus (Kier, 1958).
TUBERCLES: Primary Perforated: No (Imperforate). Distribution: Small secondary tubercles are scattered over the surface. Tubercles in interambulacra are about equal in size to those in the ambulacra.
GRANULES: See Tubercles.
FASCIOLE: Absent.
INTERAMB: Width: Narrower than ambulacra at the ambitus. Arrangement: Composed of 3 columns of hexagonal plates (Kier, 1958).
APICAL SYSTEM: Condition: Missing in all specimens (Kier, 1958).
PERIPROCT (ANUS): (Unknown).
PERISTOME (MOUTH): Condition: Missing. Lantern: Inclined auricles present (Kier, 1958).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
- Holotype: USNM 136486.
- Paratypes: USNM 136487, 136488, 136505. (Isolated interambulacral and ambulacral areas).
ETYMOLOGY
From the Latin parvus (small), referring to the diminutive size of the test.
REMARKS & COMPARISONS
Remarks: Kier (1958) established the genus Xenechinus for this species, noting its similarity to Melonechinus but distinguishing it by having only 3 columns of interambulacral plates (vs. 4 or more in Melonechinus) and 4 columns of ambulacral plates (vs. many in Melonechinus). It is one of the few Permian echinoids known from North America.
Comparisons:
- Melonechinus: X. parvus is much smaller and has fewer plate columns in both ambulacra and interambulacra.
