Taxonomic synopsis

Class Ophiuroidea

Order Euryalida ^{Lamarck, 1816}

Family Gorgonocephalidae ^{Ljungman, 1867}

Genus Asteroporpa Örstedt & Lütken, 1856 in ^{Lütken, 1856}

Asteroporpa (Asteroporpa) annulata (Örstedt & Lütken, 1856 in ^{Lütken, 1856})

Genus Astracme^{Döderlein, 1927}

Astracme mucronata (^{Lyman, 1869})

Genus Astrocaneum^{Döderlein, 1911}

Astrocaneum herrerai (^{Clark, 1919})

Astrocaneum spinosum (^{Lyman, 1875})

Genus Astrocyclus^{Döderlein, 1911}

Astrocyclus caecilia (^{Lütken, 1856})

Genus Astrodictyum^{Döderlein, 1927}

Astrodictyum panamense (^{Verrill, 1867})

Genus Astrogomphus^{Lyman, 1869}

Astrogomphus vallatus (^{Lyman, 1869})

Genus Astrophyton^{Fleming, 1828}

Astrophyton muricatum (^{Lamarck, 1816})

Genus Gorgonocephalus^{Leach, 1815}

Gorgonocephalus chilensis (^{Philippi, 1858})

Order Euryalida ^{Lamarck, 1816}

Diagnosis (^{O’Hara et al., 2018}): arm spine articulations with muscle and nerve openings well separated. Arm spines ventral only. Lateral arm plates devoid of ornamentation. Vertebrae with hourglass-shaped articulations.

Family Gorgonocephalidae ^{Ljungman, 1867}

Diagnosis (^{O’Hara et al., 2018}): dorsal part of the disc and arms with scales and plates, which bear thorny granules or spines. In the arms, they present Girdles of small hyaline hooks. Arms branched or simple. All vertebrae without an oral bridge. Multiple teeth in irregular columns, dental plate whole. Arm spine articulation with slit-shaped muscle opening proximally bordered by a vertical ridge, small nerve opening at a distance.

Genus Asteroporpa Örsted & Lütken 1856, in ^{Lütken, 1856}

Diagnosis (Örstedt & Lütken, 1856 in ^{Lütken, 1856}): disc with 10 short radial shields and five arms, extremely long and tightly articulated arms that are very narrow at their ventral side. Both radial shields are elevated from the arm region and covered by skin with warts and articulated hooks. Along the borders of the mouth, they exhibit sharp cone-shaped papillae. They have short hooklets underneath the arm rings.

Asteroporpa (Asteroporpa) annulata

(Örstedt and Lütken, 1856 in ^{Lütken, 1856})

Fig. 1A, Fig. 1B, Fig. 1C, Fig. 1D, Fig. 6A, Fig. 6B.

Asteroporpa (Asteroporpa) annulata Örstedt & Lütken, 1856 in ^{Lütken, 1856}: 17, Fig. 4a-d, Fig. 5a-b; ^{Lyman, 1882}: 125; ^{Verrill, 1899} (b): 320; ^{Döderlein, 1911}: 24, Fig. 2a-f; ^{Döderlein 1927}: 89; ^{Gondim et al., 2012}: 142-145, Fig. 1.

Diagnosis (^{Gondim et al., 2012}): aboral part of the disk covered by a thick skin, the radial shields and their surrounding are tumid, bar-like, extending more than half of the disk diameter, and covered by five rows of rings with sharp granules. The jaws and oral parts are covered by a thick skin and show small, flattened dermal ossicles. There are five simple arms; the dorsal and lateral surfaces of the arms are annulated, with inflated, white, and transverse rows of hooklet-bearing plates.

Scanning Electron Microscopy: Asteroporpa (Asteroporpa) annulata can be distinguished by its type of spines, which no other organism possesses. These spines have a rectangular base with five to seven spikes, the hooklets have an open and marked base, with clear edges; there are six very noticeable perforations found along the hooklet, at the secondary tooth base there is a groove, and the main hooklet is long (Fig. 6A, Fig. 6B).

Genus Astracme^{Döderlein, 1927}

Diagnosis (^{Döderlein, 1927}): disc and arms with thick spines, one madreporite; the first section of the arms exhibits many ramifications. They exhibit small tentacle pores before the first bifurcation; from one to three arm spines (small-sized), beginning before or immediately after the first arm bifurcation; all the final bifurcation are thin, with hooks and well-developed hook rows.

Astracme mucronata (^{Lyman, 1869})

Fig. 2A, Fig. 2B, Fig. 2C, Fig. 2D, Fig. 6D, Fig. 6H.

Astrophyton mucronatum^{Lyman, 1869}: 348. Gorgonocephalus mucronatus^{Lyman, 1882}: 265; ^{Verrill, 1899}: 85. Astrospartus mucronatus^{Döderlein, 1911}: 73. Astracme mucronata^{Döderlein, 1927}: 31.

Diagnosis (^{Manso, Gondim, & Ventura, 2014}): disc covered by flattened plate-shaped dermal ossicles of varied sizes and shapes, and some granules. Large radial shields, bar-like, covered flattened by plate-shaped dermal ossicles and some granules and spines; there are irregularly distributed spine-shaped dermal ossicles on the radial shield, the interradius is covered by flattened, plate-shaped dermal ossicles and some spine-shaped ossicles (similar to the radial shields). The jaw and oral part are covered with granules larger than those on the dorsal surface.

Scanning Electron Microscopy: Astracme mucronata has spines at the radial shields, which have a flat point and a narrow base (Fig. 6C). It has three different types of hooklets; there are marked differences at the base of each type of hooklet and also in the shape of it, having one and two secondary teeth (Fig. 6F, Fig. 6G, Fig. 6H).

Genus Astrocaneum^{Döderlein, 1911}

Diagnosis (^{Döderlein, 1911}): disc and arms with protuberances or thicker spines. Five madreporites. The main internal and external arm branching is lightly extended, the distal ramifications are thin, thread-shaped and the lateral ramifications are cone-shaped. The spine-shaped papillae are found along the arms, are tiny, and are observable from the third or fourth bifurcation.

Astrocaneum herrerai (^{Clark, 1919})

Fig. 2E, Fig. 2F, Fig. 2G, Fig. 2H, Fig. 6I, Fig. 6J.

Astrocynodus herrerai A.H. ^{Clark, 1919}: 638, Fig. 96. Astrocaneum herrerai.- ^{Döderlein, 1927}: 56; ^{Durán-González, Laguarda-Figueras, Solís-Marín, Buitrón-Sánchez, Ahearn, & Torres-Vega, 2005}: 5; ^{Pomory, 2007}: 3.

Diagnosis (^{Clark, 1919}): the oral side of the disc is covered by small granules, at the external half of the radial shields present crossed bands that are divided into sections and can be found diagonally across the shield. At the interradial oral side of the disc, it is covered with very small granules, among which there are bigger and brighter granules, grouped in a way that they form a mesh-like pattern.

Astrocaneum spinosum (^{Lyman, 1875})

Fig. 3A, Fig. 3B, Fig. 3C, Fig. 3D, Fig. 6K, Fig. 6L, Fig. 6M.

Astrophyton spinosum^{Lyman, 1875}: 29. Astrocaneum spinosum.- ^{Döderlein, 1911}: 92; ^{Döderlein, 1927}: 55; ^{Béarez & Bujard, 2013}: 2, Fig. 2- Fig. 3.

Diagnosis (^{Lyman, 1875}): at the aboral side of the disc they have a small row of spines that are scattered in groups of two or three, at the internal angle of each of the oral interradial spaces there is a madreporite; there are no signs of arm spines close to the base of the arm, but they appear at the fifth ramification, where there are two to three arm spines per each pore; the tentacle pores are narrowly contracted.

Scanning Electron Microscopy: The genus Astrocaneum posses oblong spines, however, between A. herrerai and A. spinosum there are differences at the tip of the hooklet; A. spinosum has a flat tip and is located at the center of the hooklet (Fig. 6L). The hooklets are the main characteristic to differentiate all species, which is why between these species (A. herrerai and A. spinosum) there is a morphological difference at the base of the hooklet, been longer with a bulky protruding base in A. herrerai (Fig. 6J).

Genus Astrocyclus^{Döderlein, 1911}

Diagnosis (^{Döderlein, 1911}): the radial shields and arms show prominent transversal bulges and slightly ramified arms. Five madreporites at the interior edge of the oral interradius, the tentacle pores are small and appear before or immediately after the first bifurcation. Each hook of the belt posses one or two secondary teeth; the arm spines are hook-shaped, they present one to two secondary teeth.

Astrocyclus caecilia (^{Lütken, 1856})

Fig. 3E, Fig. 3F, Fig. 3G, Fig. 3H, Fig. 6N, Fig. 6O.

Asterophyton caecilia^{Lütken, 1856}: 18; ^{Lyman, 1882}: 258.

Astrocyclus caecilia.- ^{Tommasi, 1970}: 13; ^{Gondim et al., 2015}: 2, Fig. 1.

Diagnosis (^{Tommasi, 1970}): slightly elevated radial shields, without spines or tubercules, only transversal lines; at the center of the disc there are big, protruding, and elongated granules. Five madreporites, each one located in an internal angle of the interradial spaces. The arms at the oral side exhibit a small and truncated arm spine, at the tip of the arms, the arm spine transforming into hook-shaped.

Genus Astrodictyum^{Döderlein, 1927}

Diagnosis (^{Döderlein, 1927}): the disc and arms exhibit bulges or thick spines; the main ramification of arms is slightly extended, the distal ramifications are thin and feather-shaped. There are five madreporites, the arm spines are uniformly found along the arms, they are small and begin at a certain distance from the disc, not before the third or fourth bifurcation.

Astrodictyum cf. panamense (^{Verrill, 1867})

Fig. 4A, Fig. 4B, Fig. 4C, Fig. 4D, Fig. 7A, Fig. 7B, Fig. 7C.

Astrophyton panamense^{Verrill, 1867}: 251. Astrocaneum panamense.- ^{Döderlein, 1911}: 95.

Diagnosis (^{Verrill, 1867}): the oral and aboral surfaces are covered by rough granules, at the radial shields and the dorsal side of the arms the granules are round and uniform in size, but on the ventral side they are flattened and larger. The aboral surface is slightly convex and has no presence of spines or tubercules. From two to three tentacle pores that are noted for being short, which begin at the third or fourth bifurcation; they exhibit small hooks, visible only at the terminal ramifications.

Genus Astrogomphus^{Lyman, 1869}

Diagnosis (^{Lyman, 1869}): radial shields narrow and short, the peripheral part presents numerous spines. Simple arms, the skin is covered by a mosaic of small granules, the segments of the arms are distinguished for having ridges, each one formed by a belt of granules, some of which are very small. The arm spines have the shape of a thorny stump, arranged in groups just above the tentacle pores.

Astrogomphus vallatus^{Lyman, 1869}

Fig. 4E, Fig. 4H, Fig. 7D, Fig. 7E, Fig. 7F, Fig. 7G.

Astrogomphus vallatus^{Lyman, 1869}: 350; ^{Durán-González et al., 2005}: 59.

Diagnosis (^{Lyman, 1869}): the entire aboral side is filled with short and thick spines, arranged in concentric rows, the radial shields have a rough and thorny appearance. Every ramification is covered by a belt of four rows of granules; the oral side of the arms is flat, they have a smooth skin that is uniformly covered by small flat granules, that look like a rugged mosaic. The interradial oral spaces are covered by small, round, and flat granules of different sizes.

Scanning Electron Microscopy: Astrogomphus vallatus presents an elongated slightly curved hooklet, with four secondary teeth, with a narrow well-defined base (Fig. 7G).

Genus Astrophyton^{Fleming, 1828}

Diagnosis (^{Fleming, 1828}): ventral disc covered only by skin, five arms divided dicotomically. At the periphery, the genital slit is long, ranging from the peripheral end of the oral shield to the lateral edge of the disc.

Astrophyton muricatum (^{Lamarck, 1816})

Fig. 5A, Fig. 5B, Fig. 5C, Fig. 5D, Fig. 7H, Fig. 7I.

Euryale muricatum^{Lamarck 1816}: 538. Astrophyton arborescens, ^{Müller & Troschel, 1842}: 124. Astrophyton muricatum.- ^{Müller & Troschel, 1842}: 122; ^{Döderlein, 1911}: 7, 18, 53, 108, Fig. 1; ^{Döderlein, 1927}: 24, 25.

Diagnosis (^{Müller & Troschel, 1842}): the radial shields stand out at the aboral side, they exhibit a thin granulation with conic spines that have a sliced tip (Fig. 5A); the arm granulation is thin and dense, covering the entire arm; the first segment of the arms do not have arm spine, only the thinner ramifications have two or three short arm spines. The oral side of the disc is characterized by having a thick arm base with few small and fine granules at the oral interradius, the arms can be exhibit either tubercules or spines.

Scanning Electron Microscopy: Astrophyton muricatum: the spines and hooklets are of two types and easily distinguished; one spine has a rectangular base and a short hooklet (Fig. 7H), meanwhile the other is curved with an ovoid base (Fig. 7I).

Genus Gorgonocephalus^{Leach, 1815}

Diagnosis (^{Leach, 1815}): it presents a convex body with five thick and dichotomic arms, the distal ramifications are thin and more bifurcated. The species have bursal slits at each side of the base of the arm’s inferior side.

Gorgonocephalus chilensis (^{Philippi, 1858})

Fig. 5E, Fig. 5F, Fig. 5G, Fig. 5H, Fig. 7J, Fig. 7K, Fig. 7L, Fig. 7M, Fig. 7N, Fig. 7O, Fig. 8A, Fig. 8B, Fig. 8C.

Astrophyton chilense^{Philippi, 1858}: 268. Astrophyton pourtalesi^{Lyman, 1875}: 28. Gorgonocephalus chilensis var. Novaezelandiae^{Mortensen 1924}: 91. Gorgonocephalus chilensis.- ^{Döderlein 1911}: 30, 105, Fig. 5; ^{Döderlein, 1927}: 30; ^{Monteiro & Tommasi, 1983}: 56, fig. 1, fig. 2, fig. 3, fig. 4, fig. 5, fig. 6.

Diagnosis (^{Philippi, 1858}): radial shields protruding; the arms spread five times, and the final ramifications are rosary-shaped, usually every bifurcation is divided again into another segment, but the ramifications are not identical. It has 12 main ramifications, the arms at the base get divided three more times.

Scanning Electron Microscopy: Gorgonocephalus chilensis has three types of spines and four types of hooklets, three of these hooklets have a secondary tooth, but the shape of the base of them is different (Fig. 7O, 8A, 8B), the fourth hooklet exhibits two secondary teeth and a narrow base (Fig. 8C), the perforations of the hooklets change in number and position (Fig. 8A, Fig. 8B, Fig. 8C).