Paracidaris texana (Whitney & Kellum, 1966)
Plate: PaTe-10
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Lake Travis County: Travis Stage: Albian
Measure: 33.6 mm Height: 21.1 mm
Specimen in photos: Collection of Michael K. Smith
Repository: Private Collection
HOLOTYPE INFO:
Holotype: UMMP 52164 (University of Michigan Museum of Paleontology) (Whitney & Kellum, 1966).
Locality: 2 miles southwest of Wimberley, Hays County, Texas.
Stratigraphy: Glen Rose Limestone (Lower Member).
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Genus: PARACIDARIS Pomel, 1883
Species: Paracidaris texana (Whitney & Kellum, 1966)
TYPE SPECIES: Cidaris florigemma Phillips, 1829
DIAGNOSIS
Test medium-sized, subglobular, and inflated. Characterized by perforate, non-crenulate primary tubercles and narrow, flexuous ambulacra. Interambulacral plates bear a single large tubercle surrounded by a distinct scrobicular ring. Extrascrobicular surfaces are densely granulated (Smith & Rader, 2009).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Glen Rose Formation.
Stratigraphic Units: Lower Cretaceous, Albian (Smith & Rader cite early Albian).
Counties: Travis, Hays.
Abundance: Rare.
DESCRIPTION
TOP: Length, width, height: 33.6 mm L × 33.6 mm W × 21.1 mm H. Top shape: Circular.
SIDE: Side shape: Inflated, ball-like; subglobular (Whitney & Kellum, 1966). Ambitus: Positioned at midpoint.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Narrow and flexuous (sinuous). Amb arrangement: Width is approximately 25% of the interambulacra. Interporiferous zone features two rows of secondary tubercles (mammillated granules) set against the pore pairs, with dense granulation between them (Whitney & Kellum, 1966).
PORE PAIRS: Arrangement: Uniserial. Shape: Round.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: No (Non-crenulate) (Smith & Rader, 2009). Interambulacral Tubercles: Very large primaries; mamelons rounded and perforated. Areolas are smooth with a raised platform, circular, and distinct.
SCROBICULAR TUBERCLES: Scrobicular ring distinct; tubercles surround the areolas, creating a raised edge around each plate.
GRANULES: Distribution: Dense granulation covers the extrascrobicular areas (outside of each plate) and along the interradial ridge. Miliary space is wide (Whitney & Kellum, 1966).
FASCIOLE: Absent in Cidaroida.
INTERAMB: Width: Four times wider than ambulacra. Arrangement: Made up of two rows of five large hexagonal plates; largest plates in the center.
APICAL SYSTEM: Size: Diameter 40% of test. Shape: Pentagonal; points of the pentagon touch the ambulacra (Whitney & Kellum, 1966).
PERIPROCT (ANUS): Condition: Not present in the figured specimen.
PERISTOME (MOUTH): Size: Medium (Whitney & Kellum, 1966); diameter 50% of test (Book Author). Shape: Subcircular/Almost round with very small notches at the ambulacra.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Michael K. Smith.
ETYMOLOGY
Named for the state of Texas.
REMARKS & COMPARISONS
Remarks: Originally described as Phyllacanthus texanus by Whitney & Kellum (1966). Smith & Rader (2009) formally reassigned this species to the genus Paracidaris Pomel, 1883, based on the presence of perforate, non-crenulate primary tubercles. The genus Phyllacanthus is restricted to the Cenozoic/Recent and is not appropriate for Cretaceous taxa.
Comparisons:
Remarks (01-2026): Gender Emendation: The specific epithet texanus (Masculine) was corrected to texana (Feminine) to comply with ICZN gender agreement rules for the genus Paracidaris. Smith & Rader used texanus, but texana is grammatically required.
Plate: PaTe-10
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Lake Travis County: Travis Stage: Albian
Measure: 33.6 mm Height: 21.1 mm
Specimen in photos: Collection of Michael K. Smith
Repository: Private Collection
HOLOTYPE INFO:
Holotype: UMMP 52164 (University of Michigan Museum of Paleontology) (Whitney & Kellum, 1966).
Locality: 2 miles southwest of Wimberley, Hays County, Texas.
Stratigraphy: Glen Rose Limestone (Lower Member).
SYNONYMY
- Phyllacanthus texanus Whitney & Kellum, 1966
- Paracidaris texanus (Whitney & Kellum) Smith & Rader, 2009
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Genus: PARACIDARIS Pomel, 1883
Species: Paracidaris texana (Whitney & Kellum, 1966)
TYPE SPECIES: Cidaris florigemma Phillips, 1829
DIAGNOSIS
Test medium-sized, subglobular, and inflated. Characterized by perforate, non-crenulate primary tubercles and narrow, flexuous ambulacra. Interambulacral plates bear a single large tubercle surrounded by a distinct scrobicular ring. Extrascrobicular surfaces are densely granulated (Smith & Rader, 2009).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Glen Rose Formation.
Stratigraphic Units: Lower Cretaceous, Albian (Smith & Rader cite early Albian).
Counties: Travis, Hays.
Abundance: Rare.
DESCRIPTION
TOP: Length, width, height: 33.6 mm L × 33.6 mm W × 21.1 mm H. Top shape: Circular.
SIDE: Side shape: Inflated, ball-like; subglobular (Whitney & Kellum, 1966). Ambitus: Positioned at midpoint.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Narrow and flexuous (sinuous). Amb arrangement: Width is approximately 25% of the interambulacra. Interporiferous zone features two rows of secondary tubercles (mammillated granules) set against the pore pairs, with dense granulation between them (Whitney & Kellum, 1966).
PORE PAIRS: Arrangement: Uniserial. Shape: Round.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: No (Non-crenulate) (Smith & Rader, 2009). Interambulacral Tubercles: Very large primaries; mamelons rounded and perforated. Areolas are smooth with a raised platform, circular, and distinct.
SCROBICULAR TUBERCLES: Scrobicular ring distinct; tubercles surround the areolas, creating a raised edge around each plate.
GRANULES: Distribution: Dense granulation covers the extrascrobicular areas (outside of each plate) and along the interradial ridge. Miliary space is wide (Whitney & Kellum, 1966).
FASCIOLE: Absent in Cidaroida.
INTERAMB: Width: Four times wider than ambulacra. Arrangement: Made up of two rows of five large hexagonal plates; largest plates in the center.
APICAL SYSTEM: Size: Diameter 40% of test. Shape: Pentagonal; points of the pentagon touch the ambulacra (Whitney & Kellum, 1966).
PERIPROCT (ANUS): Condition: Not present in the figured specimen.
PERISTOME (MOUTH): Size: Medium (Whitney & Kellum, 1966); diameter 50% of test (Book Author). Shape: Subcircular/Almost round with very small notches at the ambulacra.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from the Collection of Michael K. Smith.
ETYMOLOGY
Named for the state of Texas.
REMARKS & COMPARISONS
Remarks: Originally described as Phyllacanthus texanus by Whitney & Kellum (1966). Smith & Rader (2009) formally reassigned this species to the genus Paracidaris Pomel, 1883, based on the presence of perforate, non-crenulate primary tubercles. The genus Phyllacanthus is restricted to the Cenozoic/Recent and is not appropriate for Cretaceous taxa.
Comparisons:
- Phyllacanthus tysoni: Distinguished from P. texana by differences in granule density and plate counts (Whitney & Kellum, 1966).
Remarks (01-2026): Gender Emendation: The specific epithet texanus (Masculine) was corrected to texana (Feminine) to comply with ICZN gender agreement rules for the genus Paracidaris. Smith & Rader used texanus, but texana is grammatically required.
