Posted: Jul 9 2009
Costoanachis scutulata (Reeve, 1859) vs Costoanachis sparsa (Reeve, 1859)
Costoanachis scutulata in Florida is often mistaken for C. sparsa for two reasons. None of the most popular books (Abbott, Redfern, others) include C. scutulata. Radwin (The family Columbellidae in the western Atlantic part IIa - the Pyreninae. The Veliger 20(2): 119-133. Oct. 1, 1977.) erroneously restricted C. scutulata to Bermuda and no one yet has questioned this error in the literature.
Reeve's descriptions of these two species are useless. His descriptions were as follows:
sparsa - Shell fusiformly ovate, longitudinally finely ribbed, interstices cancellated, yellowish, sprinkled with chestnut dots and network, aperture small, lip varicose, notched at the upper part, denticulated within.
scutulata - Shell ovate, fulvous-chest-nut, promiscuously tessellated with white, whorls longitudinally ribbed, the last smooth, grooved at the base; aperture small, lip notched at the upper part,denticulated within.
However, Radwin did a pretty good job of describing the two and distinguishing between them. Following are his descriptions followed by some of my own observations, particularly the protoconch differences emphasized to me in communications from Dr. Harry Lee.
Based upon review of material collected in the Florida Keys and the Bahamas [see Redfern's C. sparsa (#414), which is an apparently misidentified C. scutulata - note the extreme simitarity between Redfern's description of his sparsa and Radwin's scutulata] is not restricted to Bermuda. There are several differing characters between the two species. However, the most reliable character that clearly distinguishes between scutulata and sparse is the protoconch.
Port Canaveral, Brevard Co., FL.
C. scutulata, Key Largo, Florida Keys
9/13/06 The adjacent illustration
presents a color variation of Costoanachis
scutulata that closely mimics C. sparsa.
Like C. sparsa a white background
predominates and some spiral grooves
are visible on later whorls. Subsutural
depression absent. This shell displays
almost all the exceptions to the more
common C. scutulata that cause confusion
with C. sparsa. However, the protoconch
tells the story. Less than two dark whorls
before the teleoconch begins.