Sinaecidaris roei Thompson, 2020
Plate: SiRo-10
Series: Upper Cretaceous Group: Washita Formation: Del Rio
Locale: Waco County: McLennan Stage: Cenomanian
Length: 21.8 mm Height: 13.0 mm
Collector: Terry Roe of Burleson, Texas
Holotype: NPL 94363
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94363.
Locality: Pit below the dam at Waco, McLennan County, Texas.
Stratigraphy: Del Rio Formation, Washita Group.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Subfamily: Stereocidarinae Lambert, 1900
Genus: SINAECIDARIS Fourtau, 1921
Species: Sinaecidaris roei Thompson, 2020
TYPE SPECIES: Sinaecidaris gauthieri Fourtau, 1921
DIAGNOSIS
A cidarid characterized by weakly crenulated, perforate tubercles and narrow extrascrobicular zones. The uppermost interambulacral plates lack primary tubercles (rudimentary). Scrobicular tubercles are undifferentiated. Distinguished from S. gauthieri by more rounded interambulacral plates and more pronounced ambulacral tubercles.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Del Rio Formation.
Stratigraphic Units: Upper Cretaceous, Cenomanian.
Counties: McLennan.
Abundance: Rare; only one specimen known.
DESCRIPTION
TOP: Length, width, height: 21.8 mm L × 13.0 mm H. Top shape: Slightly pentagonal. Top domed: Flat at pole.
SIDE: Ambitus: Positioned at midpoint. Side shape: Rounded sides.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Sinuous. Amb arrangement: Perradial zone has an outer set of small primary tubercles with mamelons and an inner set of smaller secondary tubercles. Amb width: Ambulacra are 24% the width of the interambulacra.
PORE PAIRS: Shape: Oblique. Features: Separated by a raised interporal ridge.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes (Weakly). Interambulacral Tubercles: Two rows of four plates. Uppermost plates lack primary tubercles (rudimentary) and are filled with secondary tubercles and granules (diagnostic of Stereocidarinae). Scrobicular Tubercles: Surround primary tubercles; undifferentiated. Areolas: Incised and round.
GRANULES: Distribution: A single band of granules lies above and below the contact zone of primary tubercles. Small pits and granules are present at the interradial triple contact areas between primary tubercles.
FASCIOLE: Absent in Cidaroida.
INTERAMB: Arrangement: Two rows of four plates. Shape: Plates thick; more pronouncedly rounded than in the type species.
APICAL SYSTEM: Size: Large; diameter 50% of test. Shape: Subpentagonal with wavy edges. Condition: Plates missing.
PERIPROCT (ANUS): Condition: Missing.
PERISTOME (MOUTH): Size: Diameter 40% of test. Shape: Pentagonal. Condition: Missing.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype NPL 94363. Found by Terry Roe.
ETYMOLOGY
Named after fossil collector Terry Roe of Burleson, Texas, who found the holotype.
REMARKS & COMPARISONS
Remarks: The genus Sinaecidaris was established by Fourtau (1921) for Cidarids that resemble Stereocidaris (having rudimentary upper tubercles) but possess crenulate tubercles (whereas Stereocidaris is typically non-crenulate).
Comparisons:
Plate: SiRo-10
Series: Upper Cretaceous Group: Washita Formation: Del Rio
Locale: Waco County: McLennan Stage: Cenomanian
Length: 21.8 mm Height: 13.0 mm
Collector: Terry Roe of Burleson, Texas
Holotype: NPL 94363
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL 94363.
Locality: Pit below the dam at Waco, McLennan County, Texas.
Stratigraphy: Del Rio Formation, Washita Group.
SYNONYMY
- Cidarid sp. Morgan, 2016 (p. 27, Figs. 32–34)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Cidaroidea Smith, 1984
Order: Cidaroida Claus, 1880
Family: Cidaridae Gray, 1825
Subfamily: Stereocidarinae Lambert, 1900
Genus: SINAECIDARIS Fourtau, 1921
Species: Sinaecidaris roei Thompson, 2020
TYPE SPECIES: Sinaecidaris gauthieri Fourtau, 1921
DIAGNOSIS
A cidarid characterized by weakly crenulated, perforate tubercles and narrow extrascrobicular zones. The uppermost interambulacral plates lack primary tubercles (rudimentary). Scrobicular tubercles are undifferentiated. Distinguished from S. gauthieri by more rounded interambulacral plates and more pronounced ambulacral tubercles.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Del Rio Formation.
Stratigraphic Units: Upper Cretaceous, Cenomanian.
Counties: McLennan.
Abundance: Rare; only one specimen known.
DESCRIPTION
TOP: Length, width, height: 21.8 mm L × 13.0 mm H. Top shape: Slightly pentagonal. Top domed: Flat at pole.
SIDE: Ambitus: Positioned at midpoint. Side shape: Rounded sides.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Sinuous. Amb arrangement: Perradial zone has an outer set of small primary tubercles with mamelons and an inner set of smaller secondary tubercles. Amb width: Ambulacra are 24% the width of the interambulacra.
PORE PAIRS: Shape: Oblique. Features: Separated by a raised interporal ridge.
TUBERCLES: Primary Perforated: Yes. Primary Crenulate: Yes (Weakly). Interambulacral Tubercles: Two rows of four plates. Uppermost plates lack primary tubercles (rudimentary) and are filled with secondary tubercles and granules (diagnostic of Stereocidarinae). Scrobicular Tubercles: Surround primary tubercles; undifferentiated. Areolas: Incised and round.
GRANULES: Distribution: A single band of granules lies above and below the contact zone of primary tubercles. Small pits and granules are present at the interradial triple contact areas between primary tubercles.
FASCIOLE: Absent in Cidaroida.
INTERAMB: Arrangement: Two rows of four plates. Shape: Plates thick; more pronouncedly rounded than in the type species.
APICAL SYSTEM: Size: Large; diameter 50% of test. Shape: Subpentagonal with wavy edges. Condition: Plates missing.
PERIPROCT (ANUS): Condition: Missing.
PERISTOME (MOUTH): Size: Diameter 40% of test. Shape: Pentagonal. Condition: Missing.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype NPL 94363. Found by Terry Roe.
ETYMOLOGY
Named after fossil collector Terry Roe of Burleson, Texas, who found the holotype.
REMARKS & COMPARISONS
Remarks: The genus Sinaecidaris was established by Fourtau (1921) for Cidarids that resemble Stereocidaris (having rudimentary upper tubercles) but possess crenulate tubercles (whereas Stereocidaris is typically non-crenulate).
Comparisons:
- Sinaecidaris gauthieri: S. roei has interambulacral plates that are more pronouncedly rounded. The primary ambulacral tubercles are more pronounced in S. roei, and the scrobicular tubercles are undifferentiated.
