Pseudananchys stephensoni Cooke, 1953
Plate: PsSt-10
Series: Upper Cretaceous Group: Austin Formation: Austin Chalk
Locale: Waco Gholson Road County: McLennan Stage: Santonian
Length: 48.6 mm (Smallest) Width: 47.1 mm Height: 26.2 mm
Specimen in photos: U.S.N.M. 108387A & 108387B Holotype
Collector: USGS SURVEY
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 108387 (Cooke, 1953).
Locality: USGS 13745, Waco-Gholson road, northwest of Waco, –.
Stratigraphy: Austin Chalk.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Holasteroida Durham, 1957
Family: Holasteridae Pictet, 1857
Genus: PSEUDANANCHYS Pomel, 1883
Species: Pseudananchys stephensoni Cooke, 1953
TYPE SPECIES: Ananchytes algirus Coquand, 1862
DIAGNOSIS
Test hemispherical, strongly arched above, and faintly sulcate in front. Ambulacra are narrow and subpetaloid with elongated pores. The apical system is elongate with the madreporic pores confined to the right anterior genital plate. Distinguished from P. completa by the presence of an anterior depression and the spacing of the genital pores (Cooke, 1953).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Austin
Formations: Austin Chalk.
Stratigraphic Units: Upper Cretaceous, Santonian.
Counties: McLennan.
Abundance: Rare; known from the type and two paratypes.
DESCRIPTION
TOP: Length, width, height: 48.6 mm L × 47.1 mm W × 26.2 mm H. Top shape: Hemispherical; horizontal outline subcircular. Top domed: Strongly arched above; faintly sulcate (grooved) in front.
SIDE: Side shape: Inflated.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Narrow and subpetaloid; all petals nearly alike, extending nearly to the margin. Amb arrangement: Anterior poriferous zones of paired petals are straight; posterior zones are gently curved (concave forward) (Cooke, 1953).
PORE PAIRS: Shape: Pores elongated; outer pores are longer than the inner pores.
TUBERCLES: Distribution: Small and widely scattered on the upper surface; larger and closer together underneath.
GRANULES: Distribution: A much finer tuberculation or granulation is present between the primary tubercles.
FASCIOLE: Absent in Pseudananchys.
APICAL SYSTEM: Location: Central or posterior to the center. Shape: Elongate. Genital pores: Four perforated genital plates; the anterior pair of pores is widely separated from the posterior pair. Posterior genital pores are closer together than in P. completa. Plating: Madreporic pores confined to the right anterior genital plate (Cooke, 1953).
PERIPROCT (ANUS): Location: Terminal. Visibility: Not visible from above.
PERISTOME (MOUTH): Location: Far forward. Shape: Transversely oval. Lip: Labiate behind.
SPINES: Shape: Acicular (needle-like).
SPECIMENS STUDIED & CONDITION: Holotype USNM 108387A and Paratype USNM 108387B. All known specimens are badly crushed.
ETYMOLOGY
Named in honor of Lloyd William Stephenson (1876–1962), USGS paleontologist and authority on the Cretaceous of the Gulf Coastal Plain.
REMARKS & COMPARISONS
Remarks: The type material consists of crushed specimens, making detailed morphometrics difficult. This species is assigned to Pseudananchys based on the subpetaloid ambulacra and elongate apical system.
Comparisons:
Remarks (03-26): Two specimens were collected by Lance Southwick in the Marlbrook Marl Formation of Lamar County.
Plate: PsSt-10
Series: Upper Cretaceous Group: Austin Formation: Austin Chalk
Locale: Waco Gholson Road County: McLennan Stage: Santonian
Length: 48.6 mm (Smallest) Width: 47.1 mm Height: 26.2 mm
Specimen in photos: U.S.N.M. 108387A & 108387B Holotype
Collector: USGS SURVEY
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
HOLOTYPE INFO:
Holotype: USNM 108387 (Cooke, 1953).
Locality: USGS 13745, Waco-Gholson road, northwest of Waco, –.
Stratigraphy: Austin Chalk.
SYNONYMY
- Pseudananchys stephensoni Cooke, 1953
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Holasteroida Durham, 1957
Family: Holasteridae Pictet, 1857
Genus: PSEUDANANCHYS Pomel, 1883
Species: Pseudananchys stephensoni Cooke, 1953
TYPE SPECIES: Ananchytes algirus Coquand, 1862
DIAGNOSIS
Test hemispherical, strongly arched above, and faintly sulcate in front. Ambulacra are narrow and subpetaloid with elongated pores. The apical system is elongate with the madreporic pores confined to the right anterior genital plate. Distinguished from P. completa by the presence of an anterior depression and the spacing of the genital pores (Cooke, 1953).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Austin
Formations: Austin Chalk.
Stratigraphic Units: Upper Cretaceous, Santonian.
Counties: McLennan.
Abundance: Rare; known from the type and two paratypes.
DESCRIPTION
TOP: Length, width, height: 48.6 mm L × 47.1 mm W × 26.2 mm H. Top shape: Hemispherical; horizontal outline subcircular. Top domed: Strongly arched above; faintly sulcate (grooved) in front.
SIDE: Side shape: Inflated.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Narrow and subpetaloid; all petals nearly alike, extending nearly to the margin. Amb arrangement: Anterior poriferous zones of paired petals are straight; posterior zones are gently curved (concave forward) (Cooke, 1953).
PORE PAIRS: Shape: Pores elongated; outer pores are longer than the inner pores.
TUBERCLES: Distribution: Small and widely scattered on the upper surface; larger and closer together underneath.
GRANULES: Distribution: A much finer tuberculation or granulation is present between the primary tubercles.
FASCIOLE: Absent in Pseudananchys.
APICAL SYSTEM: Location: Central or posterior to the center. Shape: Elongate. Genital pores: Four perforated genital plates; the anterior pair of pores is widely separated from the posterior pair. Posterior genital pores are closer together than in P. completa. Plating: Madreporic pores confined to the right anterior genital plate (Cooke, 1953).
PERIPROCT (ANUS): Location: Terminal. Visibility: Not visible from above.
PERISTOME (MOUTH): Location: Far forward. Shape: Transversely oval. Lip: Labiate behind.
SPINES: Shape: Acicular (needle-like).
SPECIMENS STUDIED & CONDITION: Holotype USNM 108387A and Paratype USNM 108387B. All known specimens are badly crushed.
ETYMOLOGY
Named in honor of Lloyd William Stephenson (1876–1962), USGS paleontologist and authority on the Cretaceous of the Gulf Coastal Plain.
REMARKS & COMPARISONS
Remarks: The type material consists of crushed specimens, making detailed morphometrics difficult. This species is assigned to Pseudananchys based on the subpetaloid ambulacra and elongate apical system.
Comparisons:
- Pseudananchys completa: P. stephensoni differs by having an anterior depression (sulcus), whereas P. completa lacks one. In P. stephensoni, the posterior genital pores are much closer together, and the madreporite is restricted to the right anterior genital plate (vs. separated areas in completa) (Cooke, 1953).
Remarks (03-26): Two specimens were collected by Lance Southwick in the Marlbrook Marl Formation of Lamar County.
