Proraster dalli (Clark, 1891)
Plate: PrDa-10
Series: Upper Cretaceous Group: Navarro Formation: Corsicana
Locale: San Antonio County: Bexar Stage: Maastrichtian
Length: 34.9 mm Width: 33.4 mm Height: 22.1 mm
Specimen in photo: NPL 83036 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 19115 (Clark, 1891).
Locality: Washita Creek, Bexar County, Texas (originally misidentified as "Washita division").
Stratigraphy: Corsicana Marl, Navarro Group (Cooke, 1953).
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: PRORASTER Lambert, 1895
Species: Proraster dalli (Clark, 1891)
TYPE SPECIES: Hemiaster atavus Arnaud, 1883
DIAGNOSIS
Test cordate, subhexagonal, and much depressed. Distinguished by extremely deep, sunken ambulacra (petals) separated by sharp ridges on the upper surface. The anterolateral petals are bent backward in their upper part. The posterior face is vertically truncated (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Navarro
Formations: Corsicana Marl; Nacatoch Sand (Arkansas).
Stratigraphic Units: Upper Cretaceous, Maastrichtian.
Counties: Bexar, Hunt, Kaufman, Navarro.
Abundance: Common in the Corsicana Marl.
DESCRIPTION
TOP: Length, width, height: 34.9 mm L × 33.4 mm W × 22.1 mm H. Top shape: Cordate, subhexagonal outline with distinct marginal angles. Prominent ridges cross the upper surface between the ambulacral furrows (Clark & Twitchell, 1915). Top domed: Depressed; sides decline rapidly to the base. Deep anterior sulcus grooves the margin.
SIDE: Side shape: Depressed profile. Posterior surface has a nearly vertical truncation of small area.
BOTTOM: Bottom shape: Flattened base.
AMB: Amb shape: Unequal; very deeply depressed on the upper surface (much more than in any other American species). Amb arrangement: Anterolateral pair bent backward in their upper part; long and deep. Posterolateral pair about one-half the length of the anterior pair. Unpaired Amb: Situated in the broad, deep anterior sulcus.
PORE PAIRS: Shape: Pores oval in paired ambulacra; united by a shallow furrow. Pores in unpaired ambulacrum are small and approximated. Arrangement: Poriferous zones broad in paired ambulacra, narrow in unpaired ambulacrum (Clark & Twitchell, 1915).
TUBERCLES: Primary Perforated: Yes (Mamelons distinct). Primary Crenulate: Yes. Distribution: Surface covered with small tubercles with sunken areolas. Tubercles increase in size toward the base (Clark & Twitchell, 1915).
GRANULES: Distribution: Fine microscopic granulation fills the interspaces.
FASCIOLE: Peripetalous: Present; circumscribes the petals (Cooke, 1953).
APICAL SYSTEM: Location: Posterior to the center of the upper surface. Size: Small and sunken. Type: Ethmolytic; madreporite separates posterior oculars (Cooke, 1953).
PERIPROCT (ANUS): Shape: Oval. Location: Situated on the truncated surface of the posterior border.
PERISTOME (MOUTH): Shape: Transversely oval. Location: Close to the anterior margin. Lip: Prominent posterior lip (Cooke, 1953).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83036. Collected by William R. Thompson, Jr.
ETYMOLOGY
Named in honor of William Healey Dall (1845–1927), American naturalist and paleontologist with the USGS/Smithsonian.
REMARKS & COMPARISONS
Remarks: Clark (1891) originally assigned this to Hemiaster. Lambert (1895) established Proraster for species with deeply sunken petals that partially close over. Cooke (1953) confirmed the stratigraphic position as Navarro (Corsicana), correcting the original "Washita" label which was an error in the type description.
Comparisons:
Plate: PrDa-10
Series: Upper Cretaceous Group: Navarro Formation: Corsicana
Locale: San Antonio County: Bexar Stage: Maastrichtian
Length: 34.9 mm Width: 33.4 mm Height: 22.1 mm
Specimen in photo: NPL 83036 Hypotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: USNM 19115 (Clark, 1891).
Locality: Washita Creek, Bexar County, Texas (originally misidentified as "Washita division").
Stratigraphy: Corsicana Marl, Navarro Group (Cooke, 1953).
SYNONYMY
- Hemiaster dalli Clark, 1891
- Proraster dalli (Clark) Lambert, 1895
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: PRORASTER Lambert, 1895
Species: Proraster dalli (Clark, 1891)
TYPE SPECIES: Hemiaster atavus Arnaud, 1883
DIAGNOSIS
Test cordate, subhexagonal, and much depressed. Distinguished by extremely deep, sunken ambulacra (petals) separated by sharp ridges on the upper surface. The anterolateral petals are bent backward in their upper part. The posterior face is vertically truncated (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Navarro
Formations: Corsicana Marl; Nacatoch Sand (Arkansas).
Stratigraphic Units: Upper Cretaceous, Maastrichtian.
Counties: Bexar, Hunt, Kaufman, Navarro.
Abundance: Common in the Corsicana Marl.
DESCRIPTION
TOP: Length, width, height: 34.9 mm L × 33.4 mm W × 22.1 mm H. Top shape: Cordate, subhexagonal outline with distinct marginal angles. Prominent ridges cross the upper surface between the ambulacral furrows (Clark & Twitchell, 1915). Top domed: Depressed; sides decline rapidly to the base. Deep anterior sulcus grooves the margin.
SIDE: Side shape: Depressed profile. Posterior surface has a nearly vertical truncation of small area.
BOTTOM: Bottom shape: Flattened base.
AMB: Amb shape: Unequal; very deeply depressed on the upper surface (much more than in any other American species). Amb arrangement: Anterolateral pair bent backward in their upper part; long and deep. Posterolateral pair about one-half the length of the anterior pair. Unpaired Amb: Situated in the broad, deep anterior sulcus.
PORE PAIRS: Shape: Pores oval in paired ambulacra; united by a shallow furrow. Pores in unpaired ambulacrum are small and approximated. Arrangement: Poriferous zones broad in paired ambulacra, narrow in unpaired ambulacrum (Clark & Twitchell, 1915).
TUBERCLES: Primary Perforated: Yes (Mamelons distinct). Primary Crenulate: Yes. Distribution: Surface covered with small tubercles with sunken areolas. Tubercles increase in size toward the base (Clark & Twitchell, 1915).
GRANULES: Distribution: Fine microscopic granulation fills the interspaces.
FASCIOLE: Peripetalous: Present; circumscribes the petals (Cooke, 1953).
APICAL SYSTEM: Location: Posterior to the center of the upper surface. Size: Small and sunken. Type: Ethmolytic; madreporite separates posterior oculars (Cooke, 1953).
PERIPROCT (ANUS): Shape: Oval. Location: Situated on the truncated surface of the posterior border.
PERISTOME (MOUTH): Shape: Transversely oval. Location: Close to the anterior margin. Lip: Prominent posterior lip (Cooke, 1953).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Hypotype NPL 83036. Collected by William R. Thompson, Jr.
ETYMOLOGY
Named in honor of William Healey Dall (1845–1927), American naturalist and paleontologist with the USGS/Smithsonian.
REMARKS & COMPARISONS
Remarks: Clark (1891) originally assigned this to Hemiaster. Lambert (1895) established Proraster for species with deeply sunken petals that partially close over. Cooke (1953) confirmed the stratigraphic position as Navarro (Corsicana), correcting the original "Washita" label which was an error in the type description.
Comparisons:
- Hemiaster: P. dalli is separated from other American species by the angular outline and the extreme depth of the ambulacral furrows (Clark & Twitchell, 1915).
