Pygaster sp. Agassiz, 1836
Plate: PySp-20
Series: Cretaceous Group: Unknown Formation: Unknown
Locale: South Llano Road County: Bexar
Length: 15.4 mm Height: 9.3 mm
Specimen in photos: U.S.N.M. 460425
Collector: Ferdinand Roemer (Historical)
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
FIGURED SPECIMEN INFO:
Specimen: USNM 460425 (Roemer Collection).
Locality: "South Llano Road," Bexar County, Texas.
Stratigraphy: Cretaceous (likely Fredericksburg Group based on associated fauna).
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Order: Pygasteroida Durham & Melville, 1957
Family: Pygasteridae Lambert, 1900
Genus: PYGASTER L. Agassiz, 1836
Species: Pygaster sp.
TYPE SPECIES: Clypeus semisulcatus Phillips, 1829
DIAGNOSIS
A small, pentagonal, and inflated Pygaster. Characterized by a very large peristome (50% of test diameter) with rounded notches.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg (Inferred).
Formations: Unknown; possibly Edwards or Comanche Peak.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Bexar.
Abundance: Rare; known from a single historical specimen.
Associated Fauna: Original label states found with Coenholectypus planatus.
DESCRIPTION
TOP: Length, width, height: 15.4 mm L × 9.3 mm H. Top shape: Pentagonal.
SIDE: Ambitus: Positioned at midpoint. Side shape: Inflated.
AMB: Amb shape: Lanceolate; widest at ambitus. Amb arrangement: Pore pairs are round and uniserial. Pore pairs become offset near the peristome. Amb width: Interambulacra are 2.25 times wider than ambulacra.
PORE PAIRS: Arrangement: Uniserial.
TUBERCLES: Primary Perforated: Yes. Condition: Specimen surface is in poor condition; details obscure.
FASCIOLE: Absent in Pygasteridae.
APICAL SYSTEM: Condition: Missing.
PERIPROCT (ANUS): Condition: Unknown (area missing or obscured).
PERISTOME (MOUTH): Size: Very large; diameter equals 50% of test diameter. Lip: Notches are large, very rounded, and about equally spaced.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied: USNM 460425 (Roemer Collection).
REMARKS & COMPARISONS
Remarks: This specimen originates from the historical collection of Ferdinand Roemer. The original label indicates it was found on the "Llano Road" in Bexar County in association with Coenholectypus planatus. Since C. planatus is an index fossil for the Fredericksburg Group (Albian), this specimen is likely of Early Cretaceous age, despite the generic description by Van Der Hoeven (1856) noting that most Pygaster are Jurassic.
Generic Note: Van Der Hoeven (1856) describes the genus generally as having a depressed body, orbicular or sub-angular outline, concave base, and a large superior anus situated in a broad furrow.
Plate: PySp-20
Series: Cretaceous Group: Unknown Formation: Unknown
Locale: South Llano Road County: Bexar
Length: 15.4 mm Height: 9.3 mm
Specimen in photos: U.S.N.M. 460425
Collector: Ferdinand Roemer (Historical)
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
FIGURED SPECIMEN INFO:
Specimen: USNM 460425 (Roemer Collection).
Locality: "South Llano Road," Bexar County, Texas.
Stratigraphy: Cretaceous (likely Fredericksburg Group based on associated fauna).
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Order: Pygasteroida Durham & Melville, 1957
Family: Pygasteridae Lambert, 1900
Genus: PYGASTER L. Agassiz, 1836
Species: Pygaster sp.
TYPE SPECIES: Clypeus semisulcatus Phillips, 1829
DIAGNOSIS
A small, pentagonal, and inflated Pygaster. Characterized by a very large peristome (50% of test diameter) with rounded notches.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Fredericksburg (Inferred).
Formations: Unknown; possibly Edwards or Comanche Peak.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Bexar.
Abundance: Rare; known from a single historical specimen.
Associated Fauna: Original label states found with Coenholectypus planatus.
DESCRIPTION
TOP: Length, width, height: 15.4 mm L × 9.3 mm H. Top shape: Pentagonal.
SIDE: Ambitus: Positioned at midpoint. Side shape: Inflated.
AMB: Amb shape: Lanceolate; widest at ambitus. Amb arrangement: Pore pairs are round and uniserial. Pore pairs become offset near the peristome. Amb width: Interambulacra are 2.25 times wider than ambulacra.
PORE PAIRS: Arrangement: Uniserial.
TUBERCLES: Primary Perforated: Yes. Condition: Specimen surface is in poor condition; details obscure.
FASCIOLE: Absent in Pygasteridae.
APICAL SYSTEM: Condition: Missing.
PERIPROCT (ANUS): Condition: Unknown (area missing or obscured).
PERISTOME (MOUTH): Size: Very large; diameter equals 50% of test diameter. Lip: Notches are large, very rounded, and about equally spaced.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied: USNM 460425 (Roemer Collection).
REMARKS & COMPARISONS
Remarks: This specimen originates from the historical collection of Ferdinand Roemer. The original label indicates it was found on the "Llano Road" in Bexar County in association with Coenholectypus planatus. Since C. planatus is an index fossil for the Fredericksburg Group (Albian), this specimen is likely of Early Cretaceous age, despite the generic description by Van Der Hoeven (1856) noting that most Pygaster are Jurassic.
Generic Note: Van Der Hoeven (1856) describes the genus generally as having a depressed body, orbicular or sub-angular outline, concave base, and a large superior anus situated in a broad furrow.
