Nucleolites texanus (Clark, 1891)
Plate: NuTe-10
Series: Upper Cretaceous Group: Austin Formation: Austin Chalk
Locale: Austin County: Travis Stage: Santonian
Length: 18.9 mm Width: 16.6 mm Height: 9.3 mm
Specimen in photos: U.S.N.M. 20266 Holotype
Collector: USGS SURVEY
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
Plate: NuTe-20
Series: Upper Cretaceous Group: Austin Formation: Austin Chalk
Locale: Blewitt County: Uvalde Stage: Santonian
Length: 18.9 mm Width: 16.6 mm Height: 9.3 mm
Collector: William Thompson
Repository: Personal Collection
HOLOTYPE INFO:
Holotype: USNM 20266 (Clark, 1891).
Locality: Austin, Travis County, Texas.
Stratigraphy: Austin Chalk.
SYNONYMY
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Cassiduloida Claus, 1880
Family: Nucleolitidae L. Agassiz & Desor, 1847
Genus: NUCLEOLITES Lamarck, 1801
Species: Nucleolites texanus (Clark, 1891)
TYPE SPECIES: Nucleolites scutatus Lamarck, 1816
DIAGNOSIS
Test ovate, rounded anteriorly, and subquadrate posteriorly. Upper surface convex; base concave. Apical system and apex are eccentric anteriorly. Periproct is small, oval, and situated in a narrow sulcus that begins some distance below the apical disc (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Austin
Formations: Austin Chalk.
Stratigraphic Units: Upper Cretaceous, Santonian.
Counties: Travis.
Abundance: Rare; known from the holotype.
DESCRIPTION
TOP: Length, width, height: 18.9 mm L × 16.6 mm W × 9.3 mm H.
Top shape: Ovate; rounded anteriorly, broader and subquadrate posteriorly.
Top domed: Convex, but more or less compressed. Apex is positioned forward of the center.
SIDE: Side shape: (Not fully described due to damage on sides of holotype).
BOTTOM: Bottom shape: Concave.
AMB: Amb shape: Narrowly lanceolate.
Amb arrangement: Subpetaloidal for a short distance from the apical system. The posterior ambulacra are much longer than the others; the unpaired anterior ambulacrum is the shortest (Clark & Twitchell, 1915).
PORE PAIRS: Shape: Oval.
Arrangement: Pores are set at an angle to one another.
TUBERCLES: Distribution: Interambulacral plates covered with irregularly arranged tubercles.
GRANULES: Distribution: Microscopic granulation covers the surface between the tubercles.
FASCIOLE: (Absent in Nucleolites).
APICAL SYSTEM: Location: Small; situated forward of the center (eccentric anteriorly).
Condition: Individual plates not distinguishable in the holotype.
PERIPROCT (ANUS): Shape: Small and oval.
Location: Supramarginal; situated in a narrow sulcus (anal groove) that begins some distance posterior to the apical system.
PERISTOME (MOUTH): Location: Situated forward of the center of the base (eccentric anteriorly).
Size: Apparently small (obscured in holotype).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 20266. Specimen is somewhat damaged on the sides; ambital outline is incomplete.
ETYMOLOGY
Named for the state of Texas, the type locality.
REMARKS & COMPARISONS
Remarks: Originally described as Echinobrissus texanus by Clark (1891). Echinobrissus is generally considered a synonym of Nucleolites in modern taxonomy. This species is distinguished by its small size, anterior eccentricity of the apical system, and the specific position of the anal sulcus.
Remarks (01-2026): Another specimen was found in Uvalde County by William Thompson.
Plate: NuTe-10
Series: Upper Cretaceous Group: Austin Formation: Austin Chalk
Locale: Austin County: Travis Stage: Santonian
Length: 18.9 mm Width: 16.6 mm Height: 9.3 mm
Specimen in photos: U.S.N.M. 20266 Holotype
Collector: USGS SURVEY
Repository: Paleobiology Dept., NMNH, Smithsonian Institution
Plate: NuTe-20
Series: Upper Cretaceous Group: Austin Formation: Austin Chalk
Locale: Blewitt County: Uvalde Stage: Santonian
Length: 18.9 mm Width: 16.6 mm Height: 9.3 mm
Collector: William Thompson
Repository: Personal Collection
HOLOTYPE INFO:
Holotype: USNM 20266 (Clark, 1891).
Locality: Austin, Travis County, Texas.
Stratigraphy: Austin Chalk.
SYNONYMY
- Echinobrissus texanus Clark, 1891
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Cassiduloida Claus, 1880
Family: Nucleolitidae L. Agassiz & Desor, 1847
Genus: NUCLEOLITES Lamarck, 1801
Species: Nucleolites texanus (Clark, 1891)
TYPE SPECIES: Nucleolites scutatus Lamarck, 1816
DIAGNOSIS
Test ovate, rounded anteriorly, and subquadrate posteriorly. Upper surface convex; base concave. Apical system and apex are eccentric anteriorly. Periproct is small, oval, and situated in a narrow sulcus that begins some distance below the apical disc (Clark & Twitchell, 1915).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Austin
Formations: Austin Chalk.
Stratigraphic Units: Upper Cretaceous, Santonian.
Counties: Travis.
Abundance: Rare; known from the holotype.
DESCRIPTION
TOP: Length, width, height: 18.9 mm L × 16.6 mm W × 9.3 mm H.
Top shape: Ovate; rounded anteriorly, broader and subquadrate posteriorly.
Top domed: Convex, but more or less compressed. Apex is positioned forward of the center.
SIDE: Side shape: (Not fully described due to damage on sides of holotype).
BOTTOM: Bottom shape: Concave.
AMB: Amb shape: Narrowly lanceolate.
Amb arrangement: Subpetaloidal for a short distance from the apical system. The posterior ambulacra are much longer than the others; the unpaired anterior ambulacrum is the shortest (Clark & Twitchell, 1915).
PORE PAIRS: Shape: Oval.
Arrangement: Pores are set at an angle to one another.
TUBERCLES: Distribution: Interambulacral plates covered with irregularly arranged tubercles.
GRANULES: Distribution: Microscopic granulation covers the surface between the tubercles.
FASCIOLE: (Absent in Nucleolites).
APICAL SYSTEM: Location: Small; situated forward of the center (eccentric anteriorly).
Condition: Individual plates not distinguishable in the holotype.
PERIPROCT (ANUS): Shape: Small and oval.
Location: Supramarginal; situated in a narrow sulcus (anal groove) that begins some distance posterior to the apical system.
PERISTOME (MOUTH): Location: Situated forward of the center of the base (eccentric anteriorly).
Size: Apparently small (obscured in holotype).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: Holotype USNM 20266. Specimen is somewhat damaged on the sides; ambital outline is incomplete.
ETYMOLOGY
Named for the state of Texas, the type locality.
REMARKS & COMPARISONS
Remarks: Originally described as Echinobrissus texanus by Clark (1891). Echinobrissus is generally considered a synonym of Nucleolites in modern taxonomy. This species is distinguished by its small size, anterior eccentricity of the apical system, and the specific position of the anal sulcus.
Remarks (01-2026): Another specimen was found in Uvalde County by William Thompson.
