Prionocidaris pawpawensis Thompson, 2016
Plate: PrPa-10
Series: Lower Cretaceous Group: Washita Formation: Pawpaw
Locale: Rio Vista County: Johnson Stage: Albian
Width: 22.4 mm Height: 15.0 mm
Specimen in photo: NPL 83047 Holotype
Collector: Frank Crane
University of Texas Non-vertebrate Paleo. Lab.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 83047.
Locality: Rio Vista, Johnson County, Texas.
Stratigraphy: Pawpaw Formation, Washita Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Genus: PRIONOCIDARIS A. Agassiz, 1863
Species: Prionocidaris pawpawensis Thompson, 2016
TYPE SPECIES: Cidarites pistillaris Lamarck, 1816
DIAGNOSIS
A Prionocidaris from the Lower Cretaceous of Texas characterized by round (not oval) areolas and ambulacra that are only slightly wavy. The perradial zone of the ambulacra is crowded with six rows of tubercles/granules.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Pawpaw Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Johnson.
Abundance: Rare; known from only one location.
DESCRIPTION
TOP: Length/Width: 22.4 mm diameter. Top shape: Round. Top domed: Flat.
SIDE: Side shape: Tall and inflated. Ambitus: Positioned at midpoint.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Slightly wavy (less wavy than P. granulostriata). Amb arrangement: Perradial zone is filled with two rows of marginal (primary) tubercles and four inner rows of secondary tubercles/granules.
PORE PAIRS: Arrangement: Conjugate; widely separated.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: No (Non-crenulate). Interambulacral Tubercles: Large at ambitus, reducing in size toward the apical system and peristome. Bosses are incised. Areolas: Round (not oval); less pronounced adorally. Scrobicular Tubercles: Somewhat differentiated.
GRANULES: Distribution: Dense granulation outside the scrobicular tubercles.
FASCIOLE: Absent in Cidaroida.
INTERAMB: Width: Over 6 times the width of ambulacra at the ambitus. Arrangement: Two rows of primary tubercles.
APICAL SYSTEM: Size: Diameter 47% of the width of the test. Condition: Missing in holotype; central.
PERIPROCT (ANUS): Condition: Missing.
PERISTOME (MOUTH): Size: Diameter 45% of the width of the test.
SPINES: Primary Spines: Unknown. Secondary Spines: Lanceolate, flattened, with longitudinal striations. Ambulacral Spines: Flattened and thin (about 4 times less wide than secondary spines).
SPECIMENS STUDIED & CONDITION: One specimen studied. Holotype NPL 83047. Found by Frank Crane.
ETYMOLOGY
Named after the Pawpaw Formation, the stratigraphic unit where the holotype was found.
REMARKS & COMPARISONS
Remarks: This species is assigned to Prionocidaris based on the non-crenulate tubercles and conjugate pores.
Comparisons:
Plate: PrPa-10
Series: Lower Cretaceous Group: Washita Formation: Pawpaw
Locale: Rio Vista County: Johnson Stage: Albian
Width: 22.4 mm Height: 15.0 mm
Specimen in photo: NPL 83047 Holotype
Collector: Frank Crane
University of Texas Non-vertebrate Paleo. Lab.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 83047.
Locality: Rio Vista, Johnson County, Texas.
Stratigraphy: Pawpaw Formation, Washita Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Genus: PRIONOCIDARIS A. Agassiz, 1863
Species: Prionocidaris pawpawensis Thompson, 2016
TYPE SPECIES: Cidarites pistillaris Lamarck, 1816
DIAGNOSIS
A Prionocidaris from the Lower Cretaceous of Texas characterized by round (not oval) areolas and ambulacra that are only slightly wavy. The perradial zone of the ambulacra is crowded with six rows of tubercles/granules.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Pawpaw Formation.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Johnson.
Abundance: Rare; known from only one location.
DESCRIPTION
TOP: Length/Width: 22.4 mm diameter. Top shape: Round. Top domed: Flat.
SIDE: Side shape: Tall and inflated. Ambitus: Positioned at midpoint.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Slightly wavy (less wavy than P. granulostriata). Amb arrangement: Perradial zone is filled with two rows of marginal (primary) tubercles and four inner rows of secondary tubercles/granules.
PORE PAIRS: Arrangement: Conjugate; widely separated.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: No (Non-crenulate). Interambulacral Tubercles: Large at ambitus, reducing in size toward the apical system and peristome. Bosses are incised. Areolas: Round (not oval); less pronounced adorally. Scrobicular Tubercles: Somewhat differentiated.
GRANULES: Distribution: Dense granulation outside the scrobicular tubercles.
FASCIOLE: Absent in Cidaroida.
INTERAMB: Width: Over 6 times the width of ambulacra at the ambitus. Arrangement: Two rows of primary tubercles.
APICAL SYSTEM: Size: Diameter 47% of the width of the test. Condition: Missing in holotype; central.
PERIPROCT (ANUS): Condition: Missing.
PERISTOME (MOUTH): Size: Diameter 45% of the width of the test.
SPINES: Primary Spines: Unknown. Secondary Spines: Lanceolate, flattened, with longitudinal striations. Ambulacral Spines: Flattened and thin (about 4 times less wide than secondary spines).
SPECIMENS STUDIED & CONDITION: One specimen studied. Holotype NPL 83047. Found by Frank Crane.
ETYMOLOGY
Named after the Pawpaw Formation, the stratigraphic unit where the holotype was found.
REMARKS & COMPARISONS
Remarks: This species is assigned to Prionocidaris based on the non-crenulate tubercles and conjugate pores.
Comparisons:
- Prionocidaris vendocinensis: P. pawpawensis differs by having greater variance in the size of the primary interambulacral tubercles (P. vendocinensis tubercles vary much less) and fewer tubercle rows (implied).
- Prionocidaris granulostriata: The ambulacra of P. pawpawensis are less wavy.
- Prionocidaris pistillaris: The type species has oval areolas, whereas P. pawpawensis has round areolas.
