Holanthus texanus Thompson, 2016
Plate: HoTe-10
Series: Upper Cretaceous Group: Navarro Formation: Neylandville Marl
Locale: Austin County: Travis Stage: Maastrichtian
Length: 28.6 mm Width: 25.6 mm Height: 22.5 mm
Specimen in photo: NPL 70932 Holotype
Collector: Ed Elliott
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL
Locality: Quarry in southeast Travis County, Texas (Austin).
Stratigraphy: Neylandville Marl, Navarro Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Hemiasteridae H. L. Clark, 1917
Genus: HOLANTHUS Lambert & Thiéry, 1924
Species: Holanthus texanus Thompson, 2016
TYPE SPECIES: Hemiaster hickmanni Koehler, 1914
DIAGNOSIS
A Holanthus from the Maastrichtian of Texas that is more ovate and less circular than European species. The apical system is positioned more posteriorly. The truncated posterior end is bulbous, and the tubercles are smaller than in congeneric species.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Navarro
Formations: Neylandville Marl
Stratigraphic Units: Upper Cretaceous, Maastrichtian
Counties: Travis
Abundance: Rare; only one specimen known.
DESCRIPTION
TOP: Length, width, height: 28.6 mm L × 25.6 mm W × 22.5 mm H.
Top shape: Test ovate; widest at midpoint, slightly wider anteriorly. Small anterior sulcus present.
Top domed: Top mostly flat, highly sloping. Highest point is 25% from the posterior end.
SIDE: Side shape: Posterior end very tall and truncated; anterior end small and rounded. From the posterior view, the test appears very bulbous.
Profile: Plastron juts downward anteriorly, creating a bulbous appearance.
BOTTOM: Plastron: Keel runs through the center of the plastron to the lip at the peristome.
AMB: Amb shape: Unpaired ambulacrum (III) narrow, lanceolate; extends more than halfway from apical system to margin.
Amb arrangement: Posterior paired ambulacra are long, petaloid, and open at both ends. Anterior paired ambulacra are half as long as the posterior pair and open at both ends.
INTERAMB: Shape: Plates large; interambulacral areas swollen/bulbous posteriorly.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores consist of one tiny and one large round pore per pair; pairs are widely separated.
Paired ambs: Pore pairs are slit-like. The top of the posterior petals shows less elongation than the rest.
TUBERCLES: Primary Perforated: Yes.
Primary Areola shape: Depressed.
Distribution: Largest tubercles on the bottom of the test. Most tubercles are concentrated on the adoral surface.
GRANULES: Distribution: Many tubercles/granules present above and to the sides of the peripetalous fasciole.
FASCIOLE: Peripetalous: Very pronounced, wide peripetalous fasciole encompasses the entire surface around the ambulacra.
Posterior/Subanal: Posterior fasciole pronounced.
APICAL SYSTEM: Location: Posterior of center
Genital pores: Four gonopores.
Plating: Madreporite zone located slightly right of center.
PERIPROCT (ANUS): Shape: Vertically oval.
Location: Located high on the truncated posterior face.
Features: Subanal pore pairs present on the lower part of the truncated face.
PERISTOME (MOUTH): Shape: Kidney-shaped.
Location: Located about 50% from center (anteriorly).
Lip: Labral plate narrow and long; pronounced ridge towards center. Just below the contact with the peristome, there is an inward curved indentation on either side.
Plastron: Sternal plates large, forming a very pronounced plastron.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied. Holotype NPL 70932. Found by Ed Elliott.
ETYMOLOGY
Named after the great state of Texas.
REMARKS & COMPARISONS
Remarks: This species represents a rare occurrence of Holanthus in North America.
Comparisons:
Plate: HoTe-10
Series: Upper Cretaceous Group: Navarro Formation: Neylandville Marl
Locale: Austin County: Travis Stage: Maastrichtian
Length: 28.6 mm Width: 25.6 mm Height: 22.5 mm
Specimen in photo: NPL 70932 Holotype
Collector: Ed Elliott
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
HOLOTYPE INFO:
Holotype: NPL
Locality: Quarry in southeast Travis County, Texas (Austin).
Stratigraphy: Neylandville Marl, Navarro Group.
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Atelostomata Zittel, 1879
Order: Spatangoida L. Agassiz, 1840
Family: Hemiasteridae H. L. Clark, 1917
Genus: HOLANTHUS Lambert & Thiéry, 1924
Species: Holanthus texanus Thompson, 2016
TYPE SPECIES: Hemiaster hickmanni Koehler, 1914
DIAGNOSIS
A Holanthus from the Maastrichtian of Texas that is more ovate and less circular than European species. The apical system is positioned more posteriorly. The truncated posterior end is bulbous, and the tubercles are smaller than in congeneric species.
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Navarro
Formations: Neylandville Marl
Stratigraphic Units: Upper Cretaceous, Maastrichtian
Counties: Travis
Abundance: Rare; only one specimen known.
DESCRIPTION
TOP: Length, width, height: 28.6 mm L × 25.6 mm W × 22.5 mm H.
Top shape: Test ovate; widest at midpoint, slightly wider anteriorly. Small anterior sulcus present.
Top domed: Top mostly flat, highly sloping. Highest point is 25% from the posterior end.
SIDE: Side shape: Posterior end very tall and truncated; anterior end small and rounded. From the posterior view, the test appears very bulbous.
Profile: Plastron juts downward anteriorly, creating a bulbous appearance.
BOTTOM: Plastron: Keel runs through the center of the plastron to the lip at the peristome.
AMB: Amb shape: Unpaired ambulacrum (III) narrow, lanceolate; extends more than halfway from apical system to margin.
Amb arrangement: Posterior paired ambulacra are long, petaloid, and open at both ends. Anterior paired ambulacra are half as long as the posterior pair and open at both ends.
INTERAMB: Shape: Plates large; interambulacral areas swollen/bulbous posteriorly.
PORE PAIRS: Arrangement: Unpaired ambulacrum pores consist of one tiny and one large round pore per pair; pairs are widely separated.
Paired ambs: Pore pairs are slit-like. The top of the posterior petals shows less elongation than the rest.
TUBERCLES: Primary Perforated: Yes.
Primary Areola shape: Depressed.
Distribution: Largest tubercles on the bottom of the test. Most tubercles are concentrated on the adoral surface.
GRANULES: Distribution: Many tubercles/granules present above and to the sides of the peripetalous fasciole.
FASCIOLE: Peripetalous: Very pronounced, wide peripetalous fasciole encompasses the entire surface around the ambulacra.
Posterior/Subanal: Posterior fasciole pronounced.
APICAL SYSTEM: Location: Posterior of center
Genital pores: Four gonopores.
Plating: Madreporite zone located slightly right of center.
PERIPROCT (ANUS): Shape: Vertically oval.
Location: Located high on the truncated posterior face.
Features: Subanal pore pairs present on the lower part of the truncated face.
PERISTOME (MOUTH): Shape: Kidney-shaped.
Location: Located about 50% from center (anteriorly).
Lip: Labral plate narrow and long; pronounced ridge towards center. Just below the contact with the peristome, there is an inward curved indentation on either side.
Plastron: Sternal plates large, forming a very pronounced plastron.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied. Holotype NPL 70932. Found by Ed Elliott.
ETYMOLOGY
Named after the great state of Texas.
REMARKS & COMPARISONS
Remarks: This species represents a rare occurrence of Holanthus in North America.
Comparisons:
- H. expergitus, H. hickmanni, & H. vadosus: H. texanus is more ovate and less round than these species.
- H. vadosus: H. texanus has an apical system that is more posterior, smaller tubercles on the truncated face and adorally, and a more bulbous truncated end.
