Mellita sp. L. Agassiz, 1841
Plate: MeSp-10
Series: Holocene Group: Undifferentiated Quaternary Formation: Barrier Island Deposits
Locale: Corpus Christi County: Nueces Stage: Northgrippian or Greenlandian
Length: 30.0 mm Width: 32.5 mm Height: 5.04 mm
Specimen in photos: Collection of Dave Hayward
Repository: Private Collection
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Clypeasteroida A. Agassiz, 1872
Family: Mellitidae Stefanini, 1912
Genus: MELLITA L. Agassiz, 1841
Species: Mellita sp.
TYPE SPECIES: Echinodiscus quinquiesperforatus Leske, 1778
DIAGNOSIS
A Holocene Mellita characterized by a test that is wider than long. Distinguished by the shape of the paired lunules, which are described as "squared" on the outer edges, and by the high pore-pair count in the posterior petals (40 sets).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Undifferentiated Quaternary
Formations: Barrier Island Deposits.
Stratigraphic Units: Holocene (Northgrippian or Greenlandian).
Counties: Nueces.
Abundance: Rare; described from photographs of one specimen.
DESCRIPTION
TOP: Length, width, height: 30.0 mm L × 32.5 mm W × 5.0 mm H.
Top shape: Subcircular; slightly wider than long. Slight notch present at the anterior margin and at each of the 4 ambulacral lunules.
Top domed: Apex positioned slightly anterior of center.
SIDE: Side shape: Margins thin and sharp.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Petals are petaloid and open at distal ends.
Amb arrangement: Anterior paired petals (II & IV) contain 22 sets of pores. Posterior paired petals (I & V) contain 40 sets of pores. Posterior petals are slightly longer than anterior petals, about equal in width, and flexed posteriorly/downward.
LUNULES: Five lunules total. Anterior paired elongated oval, squared on outer edge. Equally close to margin and petals. Posterior paired slightly larger than anterior lunules; inside ends oval, outside ends squared. Closer to petals than margin.
INTERAMB: Anal Lunule: Located in the posterior interambulacrum; positioned between the posterior paired ambulacra and dipping below.
PORE PAIRS: Shape: Inner pores tiny and round; outer pores elongated. Separated by a long furrow.
Arrangement: Closely spaced.
TUBERCLES: Distribution: Thick, evenly cover the entire test. Largest at margin and adorally.
Features: Small, crenulate; areoles sunken.
GRANULES: See Tubercles.
FASCIOLE: Absent.
APICAL SYSTEM: Location: Central to slightly anterior.
Genital pores: 4 genital pores.
Plating: Madreporite large and star-shaped.
PERIPROCT (ANUS): Shape: Vertically elongated.
Size: Smaller than peristome.
Location: Oral surface; situated halfway between the peristome and the unpaired (anal) lunule.
PERISTOME (MOUTH): Shape: Round.
Location: Central.
Features: Food grooves extend from the margin and from each outer lunule to the peristome.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from photographs (Collection of Dave Hayward).
REMARKS & COMPARISONS
Remarks: This specimen was described from photographs, requiring further study for formal specific assignment.
Comparisons:
Plate: MeSp-10
Series: Holocene Group: Undifferentiated Quaternary Formation: Barrier Island Deposits
Locale: Corpus Christi County: Nueces Stage: Northgrippian or Greenlandian
Length: 30.0 mm Width: 32.5 mm Height: 5.04 mm
Specimen in photos: Collection of Dave Hayward
Repository: Private Collection
SYSTEMATIC PALEONTOLOGY – TAXONOMY
Class: Echinoidea Leske, 1778
Subclass: Euechinoidea Bronn, 1860
Infraclass: Irregularia Latreille, 1825
Superorder: Neognathostomata Smith, 1981
Order: Clypeasteroida A. Agassiz, 1872
Family: Mellitidae Stefanini, 1912
Genus: MELLITA L. Agassiz, 1841
Species: Mellita sp.
TYPE SPECIES: Echinodiscus quinquiesperforatus Leske, 1778
DIAGNOSIS
A Holocene Mellita characterized by a test that is wider than long. Distinguished by the shape of the paired lunules, which are described as "squared" on the outer edges, and by the high pore-pair count in the posterior petals (40 sets).
STRATIGRAPHICAL OCCURRENCE & DISTRIBUTION
Group: Undifferentiated Quaternary
Formations: Barrier Island Deposits.
Stratigraphic Units: Holocene (Northgrippian or Greenlandian).
Counties: Nueces.
Abundance: Rare; described from photographs of one specimen.
DESCRIPTION
TOP: Length, width, height: 30.0 mm L × 32.5 mm W × 5.0 mm H.
Top shape: Subcircular; slightly wider than long. Slight notch present at the anterior margin and at each of the 4 ambulacral lunules.
Top domed: Apex positioned slightly anterior of center.
SIDE: Side shape: Margins thin and sharp.
BOTTOM: Bottom shape: Flat.
AMB: Amb shape: Petals are petaloid and open at distal ends.
Amb arrangement: Anterior paired petals (II & IV) contain 22 sets of pores. Posterior paired petals (I & V) contain 40 sets of pores. Posterior petals are slightly longer than anterior petals, about equal in width, and flexed posteriorly/downward.
LUNULES: Five lunules total. Anterior paired elongated oval, squared on outer edge. Equally close to margin and petals. Posterior paired slightly larger than anterior lunules; inside ends oval, outside ends squared. Closer to petals than margin.
INTERAMB: Anal Lunule: Located in the posterior interambulacrum; positioned between the posterior paired ambulacra and dipping below.
PORE PAIRS: Shape: Inner pores tiny and round; outer pores elongated. Separated by a long furrow.
Arrangement: Closely spaced.
TUBERCLES: Distribution: Thick, evenly cover the entire test. Largest at margin and adorally.
Features: Small, crenulate; areoles sunken.
GRANULES: See Tubercles.
FASCIOLE: Absent.
APICAL SYSTEM: Location: Central to slightly anterior.
Genital pores: 4 genital pores.
Plating: Madreporite large and star-shaped.
PERIPROCT (ANUS): Shape: Vertically elongated.
Size: Smaller than peristome.
Location: Oral surface; situated halfway between the peristome and the unpaired (anal) lunule.
PERISTOME (MOUTH): Shape: Round.
Location: Central.
Features: Food grooves extend from the margin and from each outer lunule to the peristome.
SPINES: Unknown.
SPECIMENS STUDIED & CONDITION: One specimen studied from photographs (Collection of Dave Hayward).
REMARKS & COMPARISONS
Remarks: This specimen was described from photographs, requiring further study for formal specific assignment.
Comparisons:
- Mellita quinquiesperforata: The specimen differs in lunule shape (squared outer edges) and pore counts.
- Mellita costabilei: Differs in the shape of the lunules.
