Plegiocidaris wenoensis Thompson, 2016
Plate: PlWe-10
Series: Lower Cretaceous Group: Washita Formation: Weno
Locale: Roanoke County: Denton Stage: Albian
Width: 19.7 mm Height: 11.8 mm
Specimen in photo: NPL 83045 Holotype
Collector: Frank Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 83045 .
Locality: Roanoke, Denton County, Texas.
Stratigraphy: Weno Formation, Washita Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Genus: PLEGIOCIDARIS Pomel, 1883
Species: Plegiocidaris wenoensis Thompson, 2016
TYPE SPECIES: Echinus coronatus Schlotheim, 1820
DIAGNOSIS
A Plegiocidaris from the Weno Formation characterized by an apical system (43%) that is slightly smaller than the peristome (46%). Primary tubercles are positioned closer to each other vertically than in most other species of the genus.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Weno Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Denton.
Abundance: Rare.
DESCRIPTION
TOP: Length, width, height: 19.7 mm W × 11.8 mm H. Top shape: Round. Top domed: Flat top.
SIDE: Ambitus: Positioned at midpoint (50% from the base). Side shape: Inflated with curved sides.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Flexed; narrows near apical system, widest at margin, slightly narrowing at peristome. Amb arrangement: A row of tubercles runs next to the pore pairs, followed by a row of perradial smaller tubercles and granules extending the entire length (except where narrowed aborally).
PORE PAIRS: Arrangement: Uniserial. Shape: Small and oblique. Conjugation: Strongly conjugated; joined by a groove and separated by a node.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Interambulacral Tubercles: Large at ambitus; not fully developed adorally. Areolas: Incised.
SCROBICULAR TUBERCLES: Differentiated.
GRANULES: Distribution: Plates covered in dense granules.
FASCIOLE: Absent in Cidaroida.
INTERAMB: Width: 4 times wider than ambulacra at the margin. Arrangement: Two rows of 4 plates. Sutures: Depressed.
APICAL SYSTEM: Size: Very large; diameter 43% of test width. Location: Central. Condition: Missing in holotype.
PERIPROCT (ANUS): Condition: Missing.
PERISTOME (MOUTH): Size: Diameter 46% of test width (slightly larger than apical system). Shape: Round.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype NPL 83045.
ETYMOLOGY
Named after the Weno Formation from which it was found.
REMARKS & COMPARISONS
Remarks: This species represents a Cretaceous occurrence of a genus primarily associated with the Jurassic.
Comparisons:
Plate: PlWe-10
Series: Lower Cretaceous Group: Washita Formation: Weno
Locale: Roanoke County: Denton Stage: Albian
Width: 19.7 mm Height: 11.8 mm
Specimen in photo: NPL 83045 Holotype
Collector: Frank Crane
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 83045 .
Locality: Roanoke, Denton County, Texas.
Stratigraphy: Weno Formation, Washita Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Genus: PLEGIOCIDARIS Pomel, 1883
Species: Plegiocidaris wenoensis Thompson, 2016
TYPE SPECIES: Echinus coronatus Schlotheim, 1820
DIAGNOSIS
A Plegiocidaris from the Weno Formation characterized by an apical system (43%) that is slightly smaller than the peristome (46%). Primary tubercles are positioned closer to each other vertically than in most other species of the genus.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Weno Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Denton.
Abundance: Rare.
DESCRIPTION
TOP: Length, width, height: 19.7 mm W × 11.8 mm H. Top shape: Round. Top domed: Flat top.
SIDE: Ambitus: Positioned at midpoint (50% from the base). Side shape: Inflated with curved sides.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Flexed; narrows near apical system, widest at margin, slightly narrowing at peristome. Amb arrangement: A row of tubercles runs next to the pore pairs, followed by a row of perradial smaller tubercles and granules extending the entire length (except where narrowed aborally).
PORE PAIRS: Arrangement: Uniserial. Shape: Small and oblique. Conjugation: Strongly conjugated; joined by a groove and separated by a node.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes. Interambulacral Tubercles: Large at ambitus; not fully developed adorally. Areolas: Incised.
SCROBICULAR TUBERCLES: Differentiated.
GRANULES: Distribution: Plates covered in dense granules.
FASCIOLE: Absent in Cidaroida.
INTERAMB: Width: 4 times wider than ambulacra at the margin. Arrangement: Two rows of 4 plates. Sutures: Depressed.
APICAL SYSTEM: Size: Very large; diameter 43% of test width. Location: Central. Condition: Missing in holotype.
PERIPROCT (ANUS): Condition: Missing.
PERISTOME (MOUTH): Size: Diameter 46% of test width (slightly larger than apical system). Shape: Round.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype NPL 83045.
ETYMOLOGY
Named after the Weno Formation from which it was found.
REMARKS & COMPARISONS
Remarks: This species represents a Cretaceous occurrence of a genus primarily associated with the Jurassic.
Comparisons:
- Plegiocidaris babeaui, P. bradfordensis, & P. saemanni: These Jurassic species are taller, more globular, and have more widely spaced interambulacral tubercles than P. wenoensis.
- Plegiocidaris coronata, P. fowleri, & P. crucifera: In these species, the apical system is larger than the peristome, whereas in P. wenoensis, the peristome is larger than the apical system.
