Pygorhynchus stephensoni Thompson, 2016
Plate: PySt-10
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Bergheim County: Kendall Stage: Albian
Length: 54.6 mm Width: 47.2 mm Height: 15.4 mm
Specimen in photo: NPL 70937 Holotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
Plate: PySt-20
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Bergheim County: Kendall Stage: Albian
Length: 24.3 mm Width: 22.5 mm Height: 9.8 mm
Specimen in photo: NPL 70938 Paratype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
Plate: PySt-30
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Bergheim County: Kendall Stage: Albian
Length: 8.3 mm Width: 1.3 mm
Specimen in photo: NPL 70939 Paratype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas Spines
HOLOTYPE INFO:
Holotype: NPL 70937.
Paratypes: NPL 70938 (Test), NPL 70939 (Spine) .
Locality: Bergheim, Kendall County, Texas.
Stratigraphy: Glen Rose Formation, Lower Glen Rose, Unit 2 (Marl collapse zone 3–4 feet above Toucasia hancockensis bed).
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Cassiduloida Claus, 1880
Family: Pygorhynchidae Lambert, 1905
Genus: PYGORHYNCHUS L. Agassiz, 1839
Species: Pygorhynchus stephensoni Thompson, 2016
TYPE SPECIES: Catopygus obovatus L. Agassiz, 1839
DIAGNOSIS
A Pygorhynchus from the Aptian of Texas characterized by a periproct notched into the posterior margin (inframarginal) and not visible from the aboral view. The test is only slightly inflated with rounded margins.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Lower Glen Rose Formation, Unit 2.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Kendall.
Abundance: Rare; 6 specimens found in a small geographic area.
DESCRIPTION
TOP: Length, width, height: 54.6 mm L × 47.2 mm W × 15.4 mm H. Top shape: Large, ovate, yet angular (especially posteriorly and on sides). Posterior slightly wider than anterior; widest point just posterior of midpoint. Slight indentation at the posterior margin due to the periproct notch. Top domed: Apex corresponds with the apical system.
SIDE: Profile: Anterior end is slightly taller than the posterior end. Side shape: Entire margin inflated.
BOTTOM: Bottom shape: Very concave.
AMB: Amb shape: All 5 ambulacra are petaloid, equal in width, and extend to the margin. Pointed at the apical system, narrowing slightly near the margins, then widening again (slight hourglass shape). Amb arrangement: Pore pairs in paired ambulacra are slightly en chevron; less so in the unpaired ambulacrum.
PORE PAIRS: Shape: Pairs include a small round pore and an elongated slit-shaped pore. Slits become smaller and round near the margin.
TUBERCLES: Distribution: Equal tuberculation in ambulacra and interambulacra. Very fine aborally; more pronounced adorally and near the margins. Features: Very small with sunken areolas.
GRANULES: (Not specified).
FASCIOLE: Absent.
APICAL SYSTEM: Location: Anterior of center ("Above midpoint"). Plating: Large madreporite. Genital pores: Four perforated genitals.
PERIPROCT (ANUS): Shape: Half-oval; becoming flat at the margin. Margin edge is slightly wider than its height. Location: Notched out of the posterior margin (inframarginal/marginal); cannot be seen aborally.
PERISTOME (MOUTH): Shape: Pentagonal; oblique. Size: Smaller than the periproct. Location: Situated about 30% of the test length from the anterior margin. Features: Bourrelets pronounced. Phyllodes broad and double-pored; outer series has more than twice the number of pores as the inner series.
SPINES: Shape: Shaft expands from base to a pronounced milled ring (widest part); neck above ring is narrower with striations. Shaft widens again, then narrows slightly toward the tip with further striations. Base: Concave acetabulum.
SPECIMENS STUDIED & CONDITION:
ETYMOLOGY
Named after Terry Stephenson of Lampasas, Texas, a longtime fossil collector and friend of the author.
REMARKS & COMPARISONS
Remarks: This species is distinguished by the specific position and visibility of the periproct.
Comparisons:
Plate: PySt-10
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Bergheim County: Kendall Stage: Albian
Length: 54.6 mm Width: 47.2 mm Height: 15.4 mm
Specimen in photo: NPL 70937 Holotype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
Plate: PySt-20
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Bergheim County: Kendall Stage: Albian
Length: 24.3 mm Width: 22.5 mm Height: 9.8 mm
Specimen in photo: NPL 70938 Paratype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
Plate: PySt-30
Series: Lower Cretaceous Group: Trinity Formation: Glen Rose
Locale: Bergheim County: Kendall Stage: Albian
Length: 8.3 mm Width: 1.3 mm
Specimen in photo: NPL 70939 Paratype
Collector: William R. Thompson, Jr.
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas Spines
HOLOTYPE INFO:
Holotype: NPL 70937.
Paratypes: NPL 70938 (Test), NPL 70939 (Spine) .
Locality: Bergheim, Kendall County, Texas.
Stratigraphy: Glen Rose Formation, Lower Glen Rose, Unit 2 (Marl collapse zone 3–4 feet above Toucasia hancockensis bed).
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Cassiduloida Claus, 1880
Family: Pygorhynchidae Lambert, 1905
Genus: PYGORHYNCHUS L. Agassiz, 1839
Species: Pygorhynchus stephensoni Thompson, 2016
TYPE SPECIES: Catopygus obovatus L. Agassiz, 1839
DIAGNOSIS
A Pygorhynchus from the Aptian of Texas characterized by a periproct notched into the posterior margin (inframarginal) and not visible from the aboral view. The test is only slightly inflated with rounded margins.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Trinity
Formations: Lower Glen Rose Formation, Unit 2.
Stratigraphic Units: Lower Cretaceous, Albian.
Counties: Kendall.
Abundance: Rare; 6 specimens found in a small geographic area.
DESCRIPTION
TOP: Length, width, height: 54.6 mm L × 47.2 mm W × 15.4 mm H. Top shape: Large, ovate, yet angular (especially posteriorly and on sides). Posterior slightly wider than anterior; widest point just posterior of midpoint. Slight indentation at the posterior margin due to the periproct notch. Top domed: Apex corresponds with the apical system.
SIDE: Profile: Anterior end is slightly taller than the posterior end. Side shape: Entire margin inflated.
BOTTOM: Bottom shape: Very concave.
AMB: Amb shape: All 5 ambulacra are petaloid, equal in width, and extend to the margin. Pointed at the apical system, narrowing slightly near the margins, then widening again (slight hourglass shape). Amb arrangement: Pore pairs in paired ambulacra are slightly en chevron; less so in the unpaired ambulacrum.
PORE PAIRS: Shape: Pairs include a small round pore and an elongated slit-shaped pore. Slits become smaller and round near the margin.
TUBERCLES: Distribution: Equal tuberculation in ambulacra and interambulacra. Very fine aborally; more pronounced adorally and near the margins. Features: Very small with sunken areolas.
GRANULES: (Not specified).
FASCIOLE: Absent.
APICAL SYSTEM: Location: Anterior of center ("Above midpoint"). Plating: Large madreporite. Genital pores: Four perforated genitals.
PERIPROCT (ANUS): Shape: Half-oval; becoming flat at the margin. Margin edge is slightly wider than its height. Location: Notched out of the posterior margin (inframarginal/marginal); cannot be seen aborally.
PERISTOME (MOUTH): Shape: Pentagonal; oblique. Size: Smaller than the periproct. Location: Situated about 30% of the test length from the anterior margin. Features: Bourrelets pronounced. Phyllodes broad and double-pored; outer series has more than twice the number of pores as the inner series.
SPINES: Shape: Shaft expands from base to a pronounced milled ring (widest part); neck above ring is narrower with striations. Shaft widens again, then narrows slightly toward the tip with further striations. Base: Concave acetabulum.
SPECIMENS STUDIED & CONDITION:
- Holotype NPL 70937: Adult test.
- Paratype NPL 70938: Juvenile/Small test (24.3 mm).
- Paratype NPL 70939: Spine (8.3 mm length).
ETYMOLOGY
Named after Terry Stephenson of Lampasas, Texas, a longtime fossil collector and friend of the author.
REMARKS & COMPARISONS
Remarks: This species is distinguished by the specific position and visibility of the periproct.
Comparisons:
- Pygorhynchus aragonensis: P. stephensoni lacks the truncated posterior end seen in P. aragonensis.
- Pygorhynchus obovatus: P. stephensoni differs by having the peristome positioned further from the midpoint, the periproct located much lower on the margin, and lacking the periproctal sulcus characteristic of P. obovatus.
