Linthia maverickensis Gardner, 1933
Plate: LiMa-10
Series: Paleocene Group: Midway Formation: Wills Point
Locale: Garfield County: Bastrop Stage: Selandian
Length: 19.8 mm Width: 21.0 mm Height: 13.7 mm
Specimen in photo: NPL 4623.0 Hypotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
Plate: LiMa-20
Series: Paleocene Group: Midway Formation: Wills Point
Locale: Mexia County: Limestone Stage: Selandian
Length: 13.1 mm Width: 14.0 mm Height: 10.0 mm
Specimen in photo: Collection of Frank Crane
HOLOTYPE INFO:
Holotype: Gardner's original material (likely at USNM or UT).
Locality: Maverick County, Texas (Gardner, 1933).
Stratigraphy: Wills Point Formation (?), Midway 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: Schizasteridae Lambert, 1905
Genus: LINTHIA Desor, 1853
Species: Linthia maverickensis Gardner, 1933
TYPE SPECIES: Linthia insignis (Merian, 1853)
DIAGNOSIS
Test very small, ovoid, and expanded posteriorly. The upper surface is elevated and descends obliquely toward the anterior. Distinguished from L. alabamensis by its significantly smaller size (one-third the dimensions).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Midway
Formations: Wills Point Formation.
Stratigraphic Units: Paleogene, Paleocene (Selandian).
Counties: Maverick (Type), Bastrop, Limestone.
Abundance: Rare; type material described from imperfect specimens.
DESCRIPTION
TOP: Length, width, height: 19.8 mm L × 21.0 mm W × 13.7 mm H (Hypotype NPL 4623.0).
Top shape: Ovoid, expanded posteriorly (Gardner, 1933).
Top domed: Upper surface elevated, rounding smoothly into the flattened lower surface. Maximum latitude is slightly posterior to the median horizontal (Gardner, 1933).
SIDE: Side shape: Obliquely descending toward the anterior extremity.
Profile: Maximum altitude is decidedly posterior (Gardner, 1933). Posterior margin broadly rounded or obscurely truncate.
BOTTOM: Bottom shape: Flattened (Gardner, 1933).
AMB: Amb shape: Anterior ambulacrum (III) is petaloid, much longer than the others; the groove is broad, moderately deep, and reflected in the anterior marginal reentrant.
Amb arrangement: Posterolateral grooves much shorter than the anterolateral. The area between the anterior and anterolateral ambulacra is narrow and high; the area between the antero- and posterolateral ambulacra is relatively broad and little elevated (Gardner, 1933).
Plating: Ambulacral plates very narrow; pore relations obscure.
PORE PAIRS: Visibility: Obscure in type material (Gardner, 1933).
TUBERCLES: Not described in text due to preservation.
FASCIOLE: Not explicitly noted in Gardner's description, likely due to imperfect preservation, but Linthia typically possesses peripetalous and latero-anal fascioles.
APICAL SYSTEM: Location: Eccentric (Gardner, 1933).
PERIPROCT (ANUS): Location: Very close to the posterior margin (Gardner, 1933).
PERISTOME (MOUTH): Shape: Semi-elliptical.
Location: Near the anterior margin.
Lip: Labiate (Gardner, 1933).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
ETYMOLOGY
Named for Maverick County, Texas, the locality where the species was first discovered.
REMARKS & COMPARISONS
Remarks: Gardner (1933) noted that the species was so unlike anything known at the time that it was described despite the imperfect preservation of the fossils in the area.
Comparisons:
Remarks (1-4-25):
Morphology: Gardner describes the anterior ambulacrum as "petaloid." In modern terminology for Schizasterids, the unpaired anterior ambulacrum is typically described as "sunken" with simple pores (non-petaloid), while the paired ambulacra are petaloid. Gardner's use of "petaloid" for Amb III likely refers to the distinct depressed nature of the groove in this species.
Plate: LiMa-10
Series: Paleocene Group: Midway Formation: Wills Point
Locale: Garfield County: Bastrop Stage: Selandian
Length: 19.8 mm Width: 21.0 mm Height: 13.7 mm
Specimen in photo: NPL 4623.0 Hypotype
Repository: Non-vertebrate Paleo. Lab., Univ. of Texas
Plate: LiMa-20
Series: Paleocene Group: Midway Formation: Wills Point
Locale: Mexia County: Limestone Stage: Selandian
Length: 13.1 mm Width: 14.0 mm Height: 10.0 mm
Specimen in photo: Collection of Frank Crane
HOLOTYPE INFO:
Holotype: Gardner's original material (likely at USNM or UT).
Locality: Maverick County, Texas (Gardner, 1933).
Stratigraphy: Wills Point Formation (?), Midway 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: Schizasteridae Lambert, 1905
Genus: LINTHIA Desor, 1853
Species: Linthia maverickensis Gardner, 1933
TYPE SPECIES: Linthia insignis (Merian, 1853)
DIAGNOSIS
Test very small, ovoid, and expanded posteriorly. The upper surface is elevated and descends obliquely toward the anterior. Distinguished from L. alabamensis by its significantly smaller size (one-third the dimensions).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Midway
Formations: Wills Point Formation.
Stratigraphic Units: Paleogene, Paleocene (Selandian).
Counties: Maverick (Type), Bastrop, Limestone.
Abundance: Rare; type material described from imperfect specimens.
DESCRIPTION
TOP: Length, width, height: 19.8 mm L × 21.0 mm W × 13.7 mm H (Hypotype NPL 4623.0).
Top shape: Ovoid, expanded posteriorly (Gardner, 1933).
Top domed: Upper surface elevated, rounding smoothly into the flattened lower surface. Maximum latitude is slightly posterior to the median horizontal (Gardner, 1933).
SIDE: Side shape: Obliquely descending toward the anterior extremity.
Profile: Maximum altitude is decidedly posterior (Gardner, 1933). Posterior margin broadly rounded or obscurely truncate.
BOTTOM: Bottom shape: Flattened (Gardner, 1933).
AMB: Amb shape: Anterior ambulacrum (III) is petaloid, much longer than the others; the groove is broad, moderately deep, and reflected in the anterior marginal reentrant.
Amb arrangement: Posterolateral grooves much shorter than the anterolateral. The area between the anterior and anterolateral ambulacra is narrow and high; the area between the antero- and posterolateral ambulacra is relatively broad and little elevated (Gardner, 1933).
Plating: Ambulacral plates very narrow; pore relations obscure.
PORE PAIRS: Visibility: Obscure in type material (Gardner, 1933).
TUBERCLES: Not described in text due to preservation.
FASCIOLE: Not explicitly noted in Gardner's description, likely due to imperfect preservation, but Linthia typically possesses peripetalous and latero-anal fascioles.
APICAL SYSTEM: Location: Eccentric (Gardner, 1933).
PERIPROCT (ANUS): Location: Very close to the posterior margin (Gardner, 1933).
PERISTOME (MOUTH): Shape: Semi-elliptical.
Location: Near the anterior margin.
Lip: Labiate (Gardner, 1933).
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION:
- Hypotype NPL 4623.0: Bastrop County.
- Specimen 2: Collection of Frank Crane. Limestone County.
ETYMOLOGY
Named for Maverick County, Texas, the locality where the species was first discovered.
REMARKS & COMPARISONS
Remarks: Gardner (1933) noted that the species was so unlike anything known at the time that it was described despite the imperfect preservation of the fossils in the area.
Comparisons:
- Linthia alabamensis: L. maverickensis is significantly smaller (one-third the size) than L. alabamensis Clark from the Midway Group of Alabama and Arkansas. However, both species are associated with the gastropod Volutocorbis limopsis (Gardner, 1933).
Remarks (1-4-25):
Morphology: Gardner describes the anterior ambulacrum as "petaloid." In modern terminology for Schizasterids, the unpaired anterior ambulacrum is typically described as "sunken" with simple pores (non-petaloid), while the paired ambulacra are petaloid. Gardner's use of "petaloid" for Amb III likely refers to the distinct depressed nature of the groove in this species.
