Anisaster mossomi (Cooke, 1942)
Plate: AgMo-10
Series: Oligocene Group: Catahoula Formation: Anahuac
Stage: Chattian (27.3–23.0 Ma)
Locale: Damond Mound County: Brazoria
Specimen in photo: TX 2054.1 Repository: University of Texas, Non-vertebrate Paleo. Lab
HOLOTYPE INFO:
Repository: Smithsonian National Museum of Natural History (USNM)
Catalog Number: USNM PAL 498999
Locality: Florida, USA (Suwannee Limestone)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata von Zittel, 1879
Order: Spatangoida Agassiz, 1840
Suborder: Paleopneustina Markov & Solovjev, 2001
Family: Prenasteridae Lambert, 1905
Genus: Anisaster Pomel, 1886
Type Species: Anisaster mossomi (Cooke, 1942)
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Catahoula (Cooke, 1942)
Formations: Anahuac Formation (Cooke, 1942)
Stratigraphic Units: Oligocene, Chattian (Cooke, 1942; PBDB)
Counties: Brazoria Co., TX (PBDB)
DESCRIPTION
TOP: Length, width, height: 28.7 mm × 26.5 mm × 23.5 mm (Cooke, 1942)
W/L %, W/H %, H/W %: 92.3%; 112.8%; 88.7%
Top shape: Upper surface greatly inflated; slopes steeply forward, gently posteriorly (Cooke, 1942)
Top domed: Yes—greatly inflated (Cooke, 1942)
Convexity: Moderately to strongly convex (Cooke, 1942)
Flatness: Not flat (Cooke, 1942)
Apical concavity: Apical system central (Cooke, 1942)
SIDE: Ambitus: Broadly rounded with posterior truncation (Cooke, 1942)
Side shape: Rounded; steep anterior slope (Cooke, 1942)
Side angle: Steep anterior, gentle posterior (Cooke, 1942)
Top ambitus location: Near posterior truncation housing the periproct (Cooke, 1942)
Wedge shape: Posterior truncation gives wedge-like appearance (Cooke, 1942)
Truncation: Present posteriorly (Cooke, 1942)
Ambitus vs midpoint: Broad rounded profile with periproct atop truncation (Cooke, 1942)
BOTTOM: Bottom flat: No—moderately convex (Cooke, 1942)
Bottom shape: Moderately convex with a transversely oval peristome (Cooke, 1942)
AMB: Amb shape: Petaloid ambulacra; petals moderately depressed (Cooke, 1942)
Amb width at apex: Weakly depressed and widely spaced pores (Cooke, 1942)
Amb widest location: Anterior pair diverges ~90°, narrower near apex (Cooke, 1942)
Amb width at peristome: Large, transversely oval, moderately lipped (Cooke, 1942)
Amb primary tubercles: Fine, uniform, dense (NHM Echinoid Directory)
Amb granules: Dense and uniform oral granulation (NHM Echinoid Directory)
Amb primary zones: Distally closed petals; narrow perradial zone (NHM Echinoid Directory)
INTERAMB: Interamb primary tubercles: Fine, uniform, dense (NHM Echinoid Directory)
Interamb granules: Dense and uniform (NHM Echinoid Directory)
PORE PAIRS: Shape: Elongate-oval (Cooke, 1942)
Density variation: Anterior pores narrower at apex and more widely spaced (Cooke, 1942)
Adapical arrangement: Specialized, uniserial pore pairs (NHM Echinoid Directory)
Size: Elongate-oval (Cooke, 1942)
Conjugate vs Nonconjugate: Uniserial (NHM Echinoid Directory)
FASCIOLE: Fasciole: Marginal fasciole descending below periproct; hemipetalous meets marginal behind anterior petals (Cooke, 1942). Peripetalous and lateroanal fasciole present (NHM Echinoid Directory)
Petalous fasciole: Hemipetalous (Cooke, 1942); peripetalous noted generally for Anisaster (NHM Echinoid Directory)
APICAL SYSTEM: Size / Location: Central (Cooke, 1942)
Shape: Ethmolytic disc with four genital pores (Cooke, 1942; NHM Echinoid Directory)
Genital pores: Four, grouped closely (Cooke, 1942)
Madreporite: Extends well behind the apical disc (Cooke, 1942)
PERIPROCT (ANUS): Shape & Size: Large, transversely oval (Cooke, 1942)
Location: At the top of the posterior truncation (Cooke, 1942)
PERISTOME (MOUTH): Size: Large (NHM Echinoid Directory) / Moderately lipped (Cooke, 1942)
Shape: Transversely oval to D-shaped (Cooke, 1942; NHM Echinoid Directory)
Lip: Moderately lipped (Cooke, 1942)
SIZE:
Slow-moving, shallow-infaunal deposit-feeder and detritivore in marine soft-sediment environments (PBDB)
AGE RANGE
Chattian Stage of Late Oligocene – approximately 27.3 to 23.0 Ma (International Chronostratigraphic Chart)
REMARKS & COMPARISONS
More spherical with a more anterior apex placement; deeper sunken petals; more developed anterior pore pairs compared to A. floridana and A. wilmingtonica (Cooke, 1942). Holotype and other specimens from SE U.S. (e.g., Belgrade Fm., NC – Miocene; Trent Fm., Oligocene) confirm broader geographic range (Smithsonian Collections; Kier, 1997).
ETYMOLOGY: Named for Stuart Mossom (1899–1994), a geologist with the Florida Geological Survey who contributed to the stratigraphy of the region (Cooke, 1942).
PREVIOUS NAMES: Agassizia (Anisaster) mossomi
Plate: AgMo-10
Series: Oligocene Group: Catahoula Formation: Anahuac
Stage: Chattian (27.3–23.0 Ma)
Locale: Damond Mound County: Brazoria
Specimen in photo: TX 2054.1 Repository: University of Texas, Non-vertebrate Paleo. Lab
HOLOTYPE INFO:
Repository: Smithsonian National Museum of Natural History (USNM)
Catalog Number: USNM PAL 498999
Locality: Florida, USA (Suwannee Limestone)
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata von Zittel, 1879
Order: Spatangoida Agassiz, 1840
Suborder: Paleopneustina Markov & Solovjev, 2001
Family: Prenasteridae Lambert, 1905
Genus: Anisaster Pomel, 1886
Type Species: Anisaster mossomi (Cooke, 1942)
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Catahoula (Cooke, 1942)
Formations: Anahuac Formation (Cooke, 1942)
Stratigraphic Units: Oligocene, Chattian (Cooke, 1942; PBDB)
Counties: Brazoria Co., TX (PBDB)
DESCRIPTION
TOP: Length, width, height: 28.7 mm × 26.5 mm × 23.5 mm (Cooke, 1942)
W/L %, W/H %, H/W %: 92.3%; 112.8%; 88.7%
Top shape: Upper surface greatly inflated; slopes steeply forward, gently posteriorly (Cooke, 1942)
Top domed: Yes—greatly inflated (Cooke, 1942)
Convexity: Moderately to strongly convex (Cooke, 1942)
Flatness: Not flat (Cooke, 1942)
Apical concavity: Apical system central (Cooke, 1942)
SIDE: Ambitus: Broadly rounded with posterior truncation (Cooke, 1942)
Side shape: Rounded; steep anterior slope (Cooke, 1942)
Side angle: Steep anterior, gentle posterior (Cooke, 1942)
Top ambitus location: Near posterior truncation housing the periproct (Cooke, 1942)
Wedge shape: Posterior truncation gives wedge-like appearance (Cooke, 1942)
Truncation: Present posteriorly (Cooke, 1942)
Ambitus vs midpoint: Broad rounded profile with periproct atop truncation (Cooke, 1942)
BOTTOM: Bottom flat: No—moderately convex (Cooke, 1942)
Bottom shape: Moderately convex with a transversely oval peristome (Cooke, 1942)
AMB: Amb shape: Petaloid ambulacra; petals moderately depressed (Cooke, 1942)
Amb width at apex: Weakly depressed and widely spaced pores (Cooke, 1942)
Amb widest location: Anterior pair diverges ~90°, narrower near apex (Cooke, 1942)
Amb width at peristome: Large, transversely oval, moderately lipped (Cooke, 1942)
Amb primary tubercles: Fine, uniform, dense (NHM Echinoid Directory)
Amb granules: Dense and uniform oral granulation (NHM Echinoid Directory)
Amb primary zones: Distally closed petals; narrow perradial zone (NHM Echinoid Directory)
INTERAMB: Interamb primary tubercles: Fine, uniform, dense (NHM Echinoid Directory)
Interamb granules: Dense and uniform (NHM Echinoid Directory)
PORE PAIRS: Shape: Elongate-oval (Cooke, 1942)
Density variation: Anterior pores narrower at apex and more widely spaced (Cooke, 1942)
Adapical arrangement: Specialized, uniserial pore pairs (NHM Echinoid Directory)
Size: Elongate-oval (Cooke, 1942)
Conjugate vs Nonconjugate: Uniserial (NHM Echinoid Directory)
FASCIOLE: Fasciole: Marginal fasciole descending below periproct; hemipetalous meets marginal behind anterior petals (Cooke, 1942). Peripetalous and lateroanal fasciole present (NHM Echinoid Directory)
Petalous fasciole: Hemipetalous (Cooke, 1942); peripetalous noted generally for Anisaster (NHM Echinoid Directory)
APICAL SYSTEM: Size / Location: Central (Cooke, 1942)
Shape: Ethmolytic disc with four genital pores (Cooke, 1942; NHM Echinoid Directory)
Genital pores: Four, grouped closely (Cooke, 1942)
Madreporite: Extends well behind the apical disc (Cooke, 1942)
PERIPROCT (ANUS): Shape & Size: Large, transversely oval (Cooke, 1942)
Location: At the top of the posterior truncation (Cooke, 1942)
PERISTOME (MOUTH): Size: Large (NHM Echinoid Directory) / Moderately lipped (Cooke, 1942)
Shape: Transversely oval to D-shaped (Cooke, 1942; NHM Echinoid Directory)
Lip: Moderately lipped (Cooke, 1942)
SIZE:
- Holotype Size: Length 27.0 mm (Cooke, 1942).
- Size Range: Length 25.2 mm to 27.0 mm (Cooke, 1959).
Slow-moving, shallow-infaunal deposit-feeder and detritivore in marine soft-sediment environments (PBDB)
AGE RANGE
Chattian Stage of Late Oligocene – approximately 27.3 to 23.0 Ma (International Chronostratigraphic Chart)
REMARKS & COMPARISONS
More spherical with a more anterior apex placement; deeper sunken petals; more developed anterior pore pairs compared to A. floridana and A. wilmingtonica (Cooke, 1942). Holotype and other specimens from SE U.S. (e.g., Belgrade Fm., NC – Miocene; Trent Fm., Oligocene) confirm broader geographic range (Smithsonian Collections; Kier, 1997).
ETYMOLOGY: Named for Stuart Mossom (1899–1994), a geologist with the Florida Geological Survey who contributed to the stratigraphy of the region (Cooke, 1942).
PREVIOUS NAMES: Agassizia (Anisaster) mossomi
