Palhemiaster calvini (Clark, 1893)
Plate: PaCa-10
Series: Upper Cretaceous Group: Washita Formation: Grayson
Locale: Argyle County: Denton Stage: Albian
Length: 58.3 mm Width: 51.6 mm Height: 34.9 mm
Specimen in photos: UT 21487 Type
Collector: (Not specified)
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 19131 (Originally Johns Hopkins Collection) (Clark, 1893).
Locality: Travis County, Texas (Shoal Creek) or North Texas Washita deposits.
Stratigraphy: Washita Group.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Hemiasteridae H. L. Clark, 1917
Genus: PALHEMIASTER Lambert, 1915
Species: Palhemiaster calvini (Clark, 1893)
TYPE SPECIES: Hemiaster comanchei Clark, 1915
DIAGNOSIS
Test oval, cordate, and inflated with an elevated upper surface and flat base. Ambulacra are moderately depressed. The anterior sulcus is shallow and narrow. Distinguished from P. whitei by its more elevated form, narrower sulcus, and more eccentric apical system (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Grayson Formation; Weno Formation, Pawpaw Formation (Adkins, 1920).
Stratigraphic Units: Lower Cretaceous (Albian) to Upper Cretaceous (Cenomanian).
Counties: Denton, Travis.
Abundance: Common in the Washita Group.
DESCRIPTION
TOP: Length, width, height: 58.3 mm L × 51.6 mm W × 34.9 mm H.
Top shape: Oval, cordate (Clark & Twitchell, 1915).
Top domed: Upper surface elevated; anterior sulcus is shallow, producing a feeble groove on the anterior margin.
SIDE: Side shape: Inflated. Posterior margin broadly and obliquely truncated.
BOTTOM: Bottom shape: Flat (Clark & Twitchell, 1915).
AMB: Amb shape: Narrow; moderately depressed on the upper surface.
Amb arrangement: Petals are of good length.
Unpaired Amb: Pores are small and approximated.
PORE PAIRS: Shape: Pores in the petaloid portions of the paired ambulacra are elongated and slit-like.
Arrangement: Beyond the petals, pores are very small and occupy the lower outside corner of each plate (Clark & Twitchell, 1915).
TUBERCLES: Distribution: Surface covered with small perforated tubercles, rather widely scattered.
GRANULES: Distribution: Microscopic granulation intervenes between tubercles.
FASCIOLE: Peripetalous: Present but indistinct in many specimens (Clark & Twitchell, 1915). (The presence of this fasciole distinguishes Palhemiaster/Hemiaster from Macraster).
APICAL SYSTEM: Location: Nearly central to slightly eccentric (Clark & Twitchell, 1915).
Size: Small and compact.
PERIPROCT (ANUS): Shape: Oval.
Location: Situated high on the truncated surface of the posterior margin.
PERISTOME (MOUTH): Shape: Transversely oval.
Size: Small.
Location: Situated at a distance from the anterior margin.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Specimen UT 21487 (labeled Holotype in input). Note: This specimen is significantly larger (58.3 mm) than the range given by Clark (up to 38 mm), representing a mature adult.
ETYMOLOGY
Named in honor of Samuel Calvin (1840–1911), American geologist and paleontologist.
REMARKS & COMPARISONS
Remarks: This species belongs to the Hemiaster complex. Lambert (1915) established Palhemiaster for Cretaceous hemiasterids with a distinct peripetalous fasciole but lacking a subanal fasciole.
Comparisons:
Plate: PaCa-10
Series: Upper Cretaceous Group: Washita Formation: Grayson
Locale: Argyle County: Denton Stage: Albian
Length: 58.3 mm Width: 51.6 mm Height: 34.9 mm
Specimen in photos: UT 21487 Type
Collector: (Not specified)
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 19131 (Originally Johns Hopkins Collection) (Clark, 1893).
Locality: Travis County, Texas (Shoal Creek) or North Texas Washita deposits.
Stratigraphy: Washita Group.
SYNONYMY
- Hemiaster calvini Clark, 1893
- Hemiaster (Mecaster) calvini (Clark) Cooke, 1946
- Palhemiaster calvini (Clark) Lambert, 1924
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Hemiasteridae H. L. Clark, 1917
Genus: PALHEMIASTER Lambert, 1915
Species: Palhemiaster calvini (Clark, 1893)
TYPE SPECIES: Hemiaster comanchei Clark, 1915
DIAGNOSIS
Test oval, cordate, and inflated with an elevated upper surface and flat base. Ambulacra are moderately depressed. The anterior sulcus is shallow and narrow. Distinguished from P. whitei by its more elevated form, narrower sulcus, and more eccentric apical system (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Washita
Formations: Grayson Formation; Weno Formation, Pawpaw Formation (Adkins, 1920).
Stratigraphic Units: Lower Cretaceous (Albian) to Upper Cretaceous (Cenomanian).
Counties: Denton, Travis.
Abundance: Common in the Washita Group.
DESCRIPTION
TOP: Length, width, height: 58.3 mm L × 51.6 mm W × 34.9 mm H.
Top shape: Oval, cordate (Clark & Twitchell, 1915).
Top domed: Upper surface elevated; anterior sulcus is shallow, producing a feeble groove on the anterior margin.
SIDE: Side shape: Inflated. Posterior margin broadly and obliquely truncated.
BOTTOM: Bottom shape: Flat (Clark & Twitchell, 1915).
AMB: Amb shape: Narrow; moderately depressed on the upper surface.
Amb arrangement: Petals are of good length.
Unpaired Amb: Pores are small and approximated.
PORE PAIRS: Shape: Pores in the petaloid portions of the paired ambulacra are elongated and slit-like.
Arrangement: Beyond the petals, pores are very small and occupy the lower outside corner of each plate (Clark & Twitchell, 1915).
TUBERCLES: Distribution: Surface covered with small perforated tubercles, rather widely scattered.
GRANULES: Distribution: Microscopic granulation intervenes between tubercles.
FASCIOLE: Peripetalous: Present but indistinct in many specimens (Clark & Twitchell, 1915). (The presence of this fasciole distinguishes Palhemiaster/Hemiaster from Macraster).
APICAL SYSTEM: Location: Nearly central to slightly eccentric (Clark & Twitchell, 1915).
Size: Small and compact.
PERIPROCT (ANUS): Shape: Oval.
Location: Situated high on the truncated surface of the posterior margin.
PERISTOME (MOUTH): Shape: Transversely oval.
Size: Small.
Location: Situated at a distance from the anterior margin.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Specimen UT 21487 (labeled Holotype in input). Note: This specimen is significantly larger (58.3 mm) than the range given by Clark (up to 38 mm), representing a mature adult.
ETYMOLOGY
Named in honor of Samuel Calvin (1840–1911), American geologist and paleontologist.
REMARKS & COMPARISONS
Remarks: This species belongs to the Hemiaster complex. Lambert (1915) established Palhemiaster for Cretaceous hemiasterids with a distinct peripetalous fasciole but lacking a subanal fasciole.
Comparisons:
- Palhemiaster whitei: P. calvini is distinguished by being more elevated, having a smaller/narrower anterior sulcus, and a more eccentric apical system (Clark & Twitchell, 1915).
- Macraster: Distinguished from Macraster species (which it resembles in shape) by the presence of a peripetalous fasciole.
