identifier	taxonID	type	CVterm	format	language	title	description	additionalInformationURL	UsageTerms	rights	Owner	contributor	creator	bibliographicCitation
CC63253534526E48FE98E556FE0BF91F.text	CC63253534526E48FE98E556FE0BF91F.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Degeneraster Blake & Lefebvre 2026	<div><p>Genus Degeneraster n. gen.</p><p>urn:lsid:zoobank.org:act:E94EE171-B0A1-4C5F-BB4E-315E8C23D5C0</p><p>TYPE SPECIES. — Degeneraster spenceri n. sp.</p><p>DIAGNOSIS. — Same as for type species, by monotypy.</p><p>ETYMOLOGY. — Latin, degener, departing from its kind; referring to absence and inferred phylogenetically significant loss of the marginal series; also, atypical abactinal expression; atypical development of the madreporite; potential axial enclosure of the water-vascular tissues; potential presence of podial pores; and the ambiguities these unusual expressions bring to interpretation of the early history of Asterozoa; and Greek, ἀστΉΡ, star.</p></div>	https://treatment.plazi.org/id/CC63253534526E48FE98E556FE0BF91F	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Blake, Daniel B.;Lefebvre, Bertrand	Blake, Daniel B., Lefebvre, Bertrand (2026): Degeneraster spenceri n. gen., n. sp. (Asteroidea; Ordovician) and interpretating the early history of the Asterozoa. Comptes Rendus Palevol 25 (10): 173-187, DOI: 10.5852/cr-palevol2026v25a10, URL: https://doi.org/10.5852/cr-palevol2026v25a10
CC63253534526E48FEA8E477FD5FFB29.text	CC63253534526E48FEA8E477FD5FFB29.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Degenerasteridae Blake & Lefebvre 2026	<div><p>Family DEGENERASTERIDAE n. fam.</p><p>urn:lsid:zoobank.org:act:E241ABDC-1197-4D7C-B1C1-1AA96456E1FA</p><p>TYPE AND ONLY KNOWN GENUS. — Degeneraster n. gen.</p><p>DIAGNOSIS. — Same as for type species, by monotypy.</p></div>	https://treatment.plazi.org/id/CC63253534526E48FEA8E477FD5FFB29	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Blake, Daniel B.;Lefebvre, Bertrand	Blake, Daniel B., Lefebvre, Bertrand (2026): Degeneraster spenceri n. gen., n. sp. (Asteroidea; Ordovician) and interpretating the early history of the Asterozoa. Comptes Rendus Palevol 25 (10): 173-187, DOI: 10.5852/cr-palevol2026v25a10, URL: https://doi.org/10.5852/cr-palevol2026v25a10
CC63253534526E43FEABE771FB02F9E0.text	CC63253534526E43FEABE771FB02F9E0.taxon	http://purl.org/dc/dcmitype/Text	http://rs.tdwg.org/ontology/voc/SPMInfoItems#GeneralDescription	text/html	en	Degeneraster spenceri Blake & Lefebvre 2026	<div><p>Degeneraster spenceri n. gen., n. sp.</p><p>(Figs 1; 2)</p><p>urn:lsid:zoobank.org:act: 3339267A-0574-4547-80C2-669F34FB9D33</p><p>MATERIAL EXAMINED. — Holotype. Kingdom of Morocco • AA.IST. OS.62; Eastern Anti-Atlas, Isthlou; Upper Tiouririne Formation; Late Ordovician (middle Katian) . Of the three available specimens, the holotype was designated because it is the only one of the three available specimens known from both the aboral and oral surfaces. The ossicular detail of the oral surface of paratype AA.IST. OS.34 is the best preserved of the three.</p><p>Paratypes. Kingdom of Morocco • 2 specimens: AA.IST.OS.34; AA.IST.OS.59; Eastern Anti-Atlas, Isthlou; Upper Tiouririne Formation; Late Ordovician (middle Katian) .</p><p>DERIVATION OF NAME. — Named in honor of W.K. Spencer, who recognized the complex diversity of early Asterozoa (Spencer 1914 - 1940, 1951), D. spenceri n. gen., n. sp. providing a new example.</p><p>TYPE LOCALITY AND STRATUM. — Kingdom of Morocco, eastern Anti-Atlas, Isthlou; Upper Tiouririne Formation; Late Ordovician (middle Katian).</p><p>DIAGNOSIS. — Abactinals sub-granular to plate-like, closely abutted, broadly uniform in total but individually somewhat varied in outline. Aboral ossicular differentiation (e.g., carinals, aboral circlet) not definitively recognized; scattered papular pores might be developed. Madreporite oral, offset from mouth frame, surface texture granular. Marginals not developed. Interbrachial oral surface actinals irregular in form and arrangement, those adjacent to mouth frame more plate-like, those of arm nearly granular. Axials robust; adradial ridge might enclose radial water-vascular tissues; abradial terminus of transverse ridge not flared but rather abutting a prominent facet of the adaxial. Podial receptacles large, podial pores might be present.</p><p>DESCRIPTION</p><p>Overall form five-armed, stellate, disk moderately large, low-vaulted; interbrachial angles weakly rounded, arms triangular, taper quite abrupt, arm tips rounded. R/r 2.5:1 of paratype AA.IST.OS.34. Abactinal ossicles plate-like to granular, irregular in outline, size variation limited; abactinals closely abutted, edges perhaps overlapping; respiratory papular pores possibly developed. Abactinal alignment in defined rows, either parallel to the arm axis or transverse to the axis, not recognized; primary circlet and centrale if present at most only weakly differentiated. Madreporite subcircular, located on oral interbrachial surface near to but not abutting MAO, axials, or adaxials. Ambital framework series not recognized. Axillary/ odontophore if occurring not clearly differentiated. Disk oral surface actinals plate-like, irregular, those of arm adjacent to adaxials smaller, more nearly equidimensional than those of disk interbrachia, both unlike abactinals.</p><p>Axials nearly paired across arm midline. Axials approximately equidimensional and approximately bilateral. Adradial ridge thickened, potentially enclosing water-vascular tissues; successive adradial ridges abutted, not appearing overlapping. Transverse ridge comparatively short, thickened; not flared abradially, rather directly abutting prominent facet on adaxial. Podial receptacle large, potentially opening as a podial pore rather than closed as a podial basin. Podial receptacle approximately equally shared by successive axials. Axials weakly offset aborally onto adaxials. Axials not appearing to narrow significantly approaching MAO suggesting only limited vaulting of the actinostome. MAO pair quite large, narrowly keel-shaped. Torus not recognized. Linear series of small spinelet attachment sites possibly developed on MAO edge but no enlarged accessory faceting recognized. A weakly differentiated terminal ossicle might occur. Adaxials approximately equidimensional; a prominent facet abuts the axial, lateral faceting linking adjacent adaxials thought to be present; enlarged accessory boss located centrally. Other accessories at most only weakly developed.</p><p>REMARKS</p><p>Ordinal assignment for D. spenceri n. gen., n. sp. to the Euaxosida is largely based on presence of a shallow, low-vaulted ambulacral furrow; approximately equidimensional axials with weakly defined cross-furrow articulation faceting with large podial receptacles; and robust adaxials with limited linkages to the axials (Figs 1-3 E-H; Blake 2018).</p><p>Because an ambital framework inferomarginal series is recognized in all known somasteroid genera, and because asteroids are considered derivatives of somasteroids, inferomarginal presence in the (unknown) first asteroid is assumed. A recent study of a large Early Devonian fauna from Central Victoria, Australia, treats many taxonomically diverse and morphologically complex asterozoans (Jell 2026). Because of availability of only a limited number of complex specimens that suffered varying degrees of diagenetic disruption, interpretation was difficult, the new genus and species Quarreriaster madelynae particularly so because of the small size and uniform morphology of the extraxial ossicles. In “Remarks” under the generic diagnosis (Jell 2026: 81), the inferomarginal column is noted to have been “… reduced to a single plate…” although it is also noted that the inferomarginal column might have been “indiscernible” (Jell 2026: 82). Recognition of marginal series even among some crown-group asteroids can be problematic, a definitive identification of marginals calling for tracing of the marginal series to the terminal ossicle at the arm tip, that not practical for Q. madelynae specimens. Phrasing in the description of Q. madelynae argues extraxial ossicular series alignment beyond that recognized for D. spenceri n. gen., n. sp. Unlike D. spenceri n. gen., n. sp., differentiation of abactinals and actinals is not recognized in Q. madelynae. Again, perhaps only because of preservation, marginal series were not found in Carboniferous Illusioluidia Blake &amp; Guensburg, 1989, it too assigned familial status (Blake 2018). All three species differ significantly in many aspects of morphology with similarities limited to class and ordinal-level manifestations, the loss, or potential loss of marginal series convergent.</p><p>Among most asteroids, the skeletal ambital framework provides a line of demarcation between typically distinctive aboral abactinals and oral actinals; although a skeletal framework is not recognized in D. spenceri n. gen., n. sp., abactinals and actinals are differentiated. Recognition of the family Degenerasteridae n. fam. also emphasizes differences between abactinals and actinals; the positioning and surface texture of the madreporite; and the potential presence of podial pores.</p><p>Closest affinities of the Degenerasteridae n. fam. are thought to lie with the Palasterinidae Gregory, 1899, the family revised in some detail in Blake (2018: 23). The Palasterinidae is a large and diverse compilation of genera, perhaps itself of complex ancestry.</p><p>Definitive evaluation of radial water-vascular tissue positioning among Paleozoic asteroids can require transverse views of arms, unfortunately unavailable for Degeneraster n. gen. Although preservation is difficult, an external skeletally defined water-vascular pathway is not recognized. Axial shape and arrangement suggest radial water-vascular tissues were skeletally enclosed, if so a potential holdover from somasteroids.</p><p>Form and positioning of the madreporite of Degeneraster n. gen. is like that of the somasteroid Chinianaster Thoral, 1935, again suggesting plesiomorphy.</p><p>Specifics of abactinals of Degeneraster n. gen. are unlike those known among somasteroids, but uniformity and small size are analogous, therein potentially derivative with limited change.</p><p>The ratio of arm radius to disk radius, R:r, is commonly included in taxonomic descriptions of asterozoans, and is included here; there are reservations (Tablado &amp; Calcagno 1994). Decay accompanied by compaction under a sediment load affect fossil proportions and thereby potential interpretation of life R:r, see discussions on the “buccal slit”.</p><p>A series of small openings are developed along the adradial boundary distally on one arm of a single specimen (Fig. 2E). Viewed from the arm tip and depending on how preservation is interpreted, the first several axial pairs lack a pore; the next two pairs exhibit a pore at the proximal edge of each pair; the next three pairs share a pore approximately medially, the more proximal two pores irregular; a pore of each axial of the next pair appears slightly inset from the midline; no further pore pairs are recognized on this arm. An enlarged opening occurs on an adjacent arm with a very small elliptical opening on the next-proximal axial pair (distally, Fig. 2D). Given disparities of occurrences, the openings are tentatively interpreted as diagenetic artifacts that nevertheless potentially reflect some aspect of ossicular construction.</p><p>SURVEY OF ASTEROZOAN CONFIGURATION AND CONSTRUCTION</p><p>BACKGROUND</p><p>Interpretations of skeletal homologies among early asterozoans have differed significantly among authors leading to significantly differing phylogenetic and taxonomic conclusions (e.g., Spencer 1914 -1940, 1951; Fell 1963; Spencer &amp; Wright 1966; Smith 1984, 2005; Smith &amp; Jell 1990; Mooi &amp; David 2000, 2008; Dean Shackleton 2005; Blake 2013, 2018; Telford et al. 2014; Blake et al. 2015b; Villier et al. 2018; Hunter &amp; Ortega-Hernández 2021; Blake &amp; Hotchkiss 2022; Blake &amp; Lefebvre 2025: 482). Supplementing this rich literature, ongoing new discoveries and reevaluations of Ordovician Somasteroidea, Asteroidea (e.g., Blake &amp; Lefebvre 2024), Ophiuroidea (e.g., Glass et al. 2024), and unassigned Asterozoa (e.g., Falloaster) have continued to provide significant new data addressing early asterozoan diversity and evolution. With emphasis on atypical Degeneraster n. gen., the following discussions follow the leads of earlier workers (e.g., Ubaghs 1953; Spencer &amp; Wright 1966; Dean Shackleton 2005) in developing overview of the early history of the Asterozoa .</p><p>BODY FORM</p><p>Overall body configuration provides guidance to class-level affinities among Paleozoic asterozoans, but many, including some ophiuroids (e.g., Componaster, Fig. 5I, J), are at least broadly similar and therefore form is not a definitive indicator of affinities of D. spenceri n. gen., n. sp.</p><p>THE AXIAL SKELETON: ARM AXIALS</p><p>Arm axials of D. spenceri n. gen., n. sp., like those of somasteroids, are approximately equidimensional and bilateral with the adradial ridges potentially enclosing the radial water-vascular tissues. Podial receptacles are large and approximately shared between successive ossicles; podial receptacles of D. spenceri n. gen., n. sp. potentially open as podial pores, and in that similar in appearance to the somasteroids Archegonaster, Chinianaster, and Thoralaster Dean Shackleton, 2005 (Blake &amp; Lefebvre 2025: figs 1A, F; 8F, G). Adaxial configuration and furrow presence of D. spenceri n. gen., n. sp. in contrast are typically euaxosidan.</p><p>Critical in the transition from ancestral somasteroids to basal euaxosidan asteroids was onset of axial displacement onto the adaxial as a part of the vaulting process to form the ambulacral furrow. An axial oral skeletal shield has been recognized among the unvaulted somasteroids (e.g., Fig. 3A; Blake &amp; Lefebvre 2025) that served to enclose and protect the oral surfaces of the radial water vascular tissues (skeletal shields, however, commonly were destroyed taphonomically as to expose the aboral surface of the water-vascular channel, especially so toward the thickened disk; Fig. 3B). Oral shield loss accompanied the evolution of asteroid ambulacral furrow vaulting.</p><p>The nature of podial tissue seating is important to the evaluation of asteroid history. Podial receptacles of most Paleozoic somasteroids and asteroids are skeletally closed as to yield socalled “podial basins” (“podial roof” is descriptively better), the solid “podial basin” surfaces restricting podial tissues to the exposed furrow exterior. Podial openings, “podial pores”, allowed retreat of some podial tissues into the protected disk and arm interiors. Presence of podial pores among Ordovician asteroids has been argued (e.g., Branstrator 1975), discussed, and challenged (Blake &amp; Guensburg 1988; Blake 2018: 11), challenged in part because true podial pores are clearly and uniformly sculptured whereas putative “podial pores” tend to be small and irregular in form and occurrence, and in part because putative “podial pores” typically are found near the axial-adaxial juncture where articulation is particularly weak and subject to minor displacement with sediment compaction. Although interpretation is problematic, podial pores potentially were developed in D. spenceri n. gen., n. sp. Curvature of the adradial margins of adaxials of both D. spenceri n. gen., n. sp. (Fig. 2D) and Jugiaster speciosus (Miller &amp; Dyer, 1878) (Fig. 3F) served to constrain podia; however, because of preservational limitations, possible presence of an aperture is obscure in these genera. Podial pores, however, are recognized in some later Paleozoic asteroids including the kermasidan Delicaster Blake &amp; Elliott, 2003 (Kesling 1967; Fig. 4F). A clearly illustrated Devonian occurrence was documented by Haude (1995) and reported Paleozoic occurrences were summarized (Blake 2018). Podial pores are universal among crown group Asteroidea and are developed in unassigned Falloaster (Fig. 5K). Given breadth of occurrences, podial pores are homoplastic.</p><p>In some somasteroids, the transverse ridge flares abradially to seat the virgal series, the virgalia capable of coordinated lateral flexure in the oral plane (Fig. 3B; Blake &amp; Lefebvre 2025). Some lateral flexure appears to have been retained in some euaxosidans (Fig. 3 E-G) but abandoned in the Degeneraster n. gen. lineage (Fig. 2), and flexure was entirely lost among derived asteroids, loss suggesting evolving behavioral differences perhaps including shifting from suspension to emphases on substrate-feeding (e.g., Spencer 1951: 91, 121).</p><p>Derivation of the Hadrosida from the Euaxosida continued phylogenetic displacement of axials toward the aboral surface of the adaxial (Fig. 4D, E), that of the Kermasida to a fully aboral positioning (Fig. 4F). The breadth of the axial series of relatively weakly constructed euaxosidans commonly was exposed with specimen compaction (e.g., Fig. 3E, G), whereas those of the more compaction-resistant derived Hadrosida and Kermasida are progressively more likely to approximate life configurations (Fig. 4D, E, G). The comparatively intact D. spenceri n. gen., n. sp. (Figs 1; 2) specimens are unusual among euaxosidans,perhaps reflecting unusual burial conditions or potentially unrecognized aspects of skeletal construction.</p><p>Among more derived Paleozoic asteroids, axials were foreshortened, the nearly equidimensional outline typical of euaxosidan axials (e.g., Figs 2 A-E; 3E-G) giving way to rectangular shapes (e.g., Fig. 4D). The transverse water-vascular channel of the broad euaxosidan axial commonly was exposed on the oral surface (e.g., Fig. 3 E-H) whereas the transverse channel typically is obscured in the proportionately narrow axials of derived genera (e.g., Fig. 4D). Narrowing of axials has the potential advantage of increasing podial number per unit arm length.</p><p>Axial and adaxial configurations of Componaster (Fig. 5K) are characteristic of Ophiuroidea and unlike corresponding expressions of the Asteroidea . The transverse axial ribbing and large, rimmed podial pores of Falloaster (Fig. 5K) are unique, and adaxials are lacking, placing that genus well apart from currently recognized asterozoan classes.</p><p>THE AXIAL SKELETON: MOUTH FRAME</p><p>The enlarged potentially weakly vaulted keel-like MAO of D. spenceri n. gen., n. sp. is asteroid-like and in that, unlike the mouth frames of somasteroids. As preserved, ambulacra of many somasteroids and early asteroids are dilated at the mouth frame in V-shaped configurations (e.g., Fig. 3A, C), the occurrences historically judged as reflecting life positioning and termed “buccal slits” (e.g., Spencer 1951). Presence of true “buccal slits” in life would carry significant implications for the interpretation of life mode and subphylum phylogeny; however, comparison of specimens among individuals of individual taxa, including D. spenceri n. gen., n. sp. (e.g., Figs 1F; 2A, F), among ambulacra of single individuals (Fig. 3A), of specimens among taxa (Figs 1F; 2B, G; 3A, C; 4A), and the general “buccal slit” absence from occurrences of the more robustly constructed derived asteroids (e.g., Fig. 4D, G) demonstrates that “buccal slits” are preservational artifacts produced by differential disk flattening. Based on occurrence, the Y-shaped mouth frames typical of ophiuroids (Fig. 5J) are an apomorphic derivative of somasteroids and apart from asteroid evolution.</p><p>Considerable debate has surrounded the interpretation of the homologies of the ossicles of the jaw frame, reviewed with emphasis on the Asteroidea (Mooi &amp; David 2000) and for all Asterozoa (Dean Shackleton 2005: 44). In a summation, Mooi &amp; David (2000: 336) argued “… the available evidence from both ontogeny and adult morphology suggest that the first ambulacral is at least involved in the construction of the MAO. It is possible that the first adambulacral is also part of the MAO, but there is some good evidence against this idea”.</p><p>In accord with thinking ofMooi &amp; David (2000), the MAO and immediately adjacent axials of the somasteroid Ophioxenikos Blake &amp; Guensburg, 1993, are similar in form and size (Fig. 3C), and no other ossicles appear to be incorporated into the jaw frame. Supernumerary ossicles, however, have been recognized associated with the mouth frames of the somasteroids Thoralaster and Villebrunaster Spencer, 1951 (Blake &amp; Lefebvre 2025: 458). The mouth frame of Cantabrigiaster Hunter &amp; Ortega-Hernández, 2021, incorporates both compound axials and apparent reduction of adradial adaxial number (Blake &amp; Lefebvre 2025: 469, fig. 4). Variation among basal somasteroids might indicate more than a single evolutionary sequence leading toward derived asterozoan lineages.</p><p>Although not reminiscent of any somasteroid, supernumerary ossicles also are incorporated into the mouth frame of the only known specimen of the euaxosidan “ Palaeaster ” exculptus Miller, 1881, the generic assignment tentative (Blake 2018). MAO of this specimen were flattened and dilated distally but nearly abutted toward the mouth opening (Fig. 4A, B). Two axials fully abut the MAO, the more proximal sharing a podial basin with the MAO, the basin directed toward the mouth. On the right side of the mouth frame as viewed here, a third more distal axial contacts both the MAO and a small adaxial that abuts the distal side of the MAO; configuration on the left is similar but the adaxial was lost. The “ P. ” exculptus configuration has at least two explanations, the first, that near-MAO adaxials fused with the MAO and their accompanying axials were evolutionarily displaced onto the fused MAO; and secondly, complete adaxial loss accompanied axial displacement onto a still-simple MAO. Ossicular fusion has been favored for some taxa: “The oral plate (= MAO) is seemingly a fused plate which is composed of oral plate proper and the 1 st adambulacral plate” (Hayashi &amp; Komatsu 1971: 77). Because there is no evidence of partial ossicular fusing for “ P. ” exculptus, adaxial loss accompanying axial displacement appears to provide the readier interpretation. Either process would increase podial density at the mouth frame, an outcome attained in derived lineages ( Hadrosida, Fig. 4D; Kermasida) through proportional shortening of axials, and in some lineages, vaulting of the actinostome (Fig. 4D), vaulting later strongly developed for example in the crown-group Asteriidae .</p><p>THE AXIAL SKELETON: TERMINALS</p><p>The terminal ossicle occurs at the distal tip of the arm, with axial, adaxial, marginal, and any carinal series arising at its proximal side. The terminal ossicle, although not specifically assigned to category, was implicitly treated as axial (Spencer &amp; Wright 1966: 11) and specifically so by many later authors (e.g., Mooi &amp; David 2000: 330).</p><p>Although a terminal can be recognized in some fossil asterozoans (e.g., Blake 2008: fig. 2.2, 2.3, 2.5), recognition usually is difficult because many terminals are similar in size and form to adjacent ossicles and also because arm tips are readily disrupted during preservation, thereby obscuring ossicular identification.</p><p>Terminals have not been recognized among somasteroids (e.g., Blake &amp; Lefebvre 2025). Although the best-preserved tips of D. spenceri n. gen., n. sp. appear largely intact, a terminal is possible but not definitively recognized (Fig. 2E). Although the terminal arises early during the skeletal ontogeny of extant asteroids (e.g., Kano et al. 1974; Komatsu 1975, 1982; Oguro et al. 1976; Siddall 1979), the possibility that the terminal arose phylogenetically late perhaps as a derivative of the extraxial inferomarginal series cannot be dismissed based on expressions among fossils. If the terminal is to be treated as axial or adaxial (Spencer &amp; Wright 1966) then the aligned inferomarginal series might also be argued as adaxial.</p><p>THE ADAXIAL SKELETON</p><p>The adaxial skeletal cohort consists of somasteroid virgalia; stenuroid embedded and outer virgals; asteroid adambulacrals; and ophiuroid laterals. Although earlier favored (Spencer 1951; Spencer &amp; Wright 1966), the ambital framework is not adaxial (Blake 2024; Blake &amp; Lefebvre 2025). Euaxosidan adaxials and axials are comparatively weakly articulated, the adaxials commonly (e.g., Figs 2D; 3G; 4A) but not always (e.g., Fig. 3E, F) approximately equidimensional; among derived hadrosidans and kermasidans, axials and adaxials are more strongly and closely articulated (e.g., Fig. 4 D-G) and adaxials generally are approximately equidimensional. Adaxial expression of the superficially asteroid-like Componaster (Fig. 5J) is typical of ophiuroids, whereas superficially asteroid-like Falloaster (Fig. 5K) lacks adaxials. The literature on adaxials was reviewed in Blake (2018: 7).</p><p>THE EXTRAXIAL SKELETON: ABACTINALS</p><p>Abactinals of somasteroids and many early asteroids are intraspecifically uniform, the ossicles small, closely spaced, and not differentiated into carinal series, an aboral circlet, or centrale (e.g., Fig. 5D, F). Abactinal differentiation arose promptly during asteroid evolution (e.g., Fig. 5G), the broad taxonomic distribution of occurrences indicating homoplasy, with carinals argued under a specified constructional constraint (Blake &amp; Rozhnov 2007: 526).</p><p>Abactinals of D. spenceri n. gen., n. sp., like those of somasteroids, are small and uniform, but with specifics of shape and arrangement diagnostic for this species. The only available aboral disk surface of D. spenceri n. gen., n. sp. suggests limited and perhaps phylogenetically emergent differentiation of a primary circlet and centrale (Fig. 1A), and in this, a step beyond somasteroids; aspects of the appearance of the D. spenceri n. gen., n. sp. abactinal skeleton, however, might reflect preservation.</p><p>The enlarged, abutted plate-like abactinals of the ophiuroid Componaster (Fig. 5I) are comparable to those of some derived asteroids indicating homoplasy among diverse asterozoan lineages.</p><p>THE EXTRAXIAL SKELETON: MADREPORITE</p><p>Madreporite variation among both somasteroids and derived asterozoans was significant, arguing homoplastic emergence of a robust calcified condition from an at most weakly calcified ancestral hydropore. Whether because of homoplasy, limitations of preservation, or absence, a madreporite has not been recorded from many early asterozoans, but where recognized, madreporites are varied in position and surface textures (e.g., Figs 1F, G; 4G; 5D, E, K).</p><p>The granular surface texture and a positioning offset from the MAO of the D. spenceri n. gen., n. sp. madreporite correspond with expressions of the somasteroid Chinianaster . In contrast, aboral positioning and the ridge-and-groove texture of the somasteroid Archegonaster (Smith &amp; Jell 1990) are similar to those of Estoniaster (Fig. 5E). Lateral madreporite positioning among Paleozoic asterozoans (e.g., Figs 4G; 5D, K) is of uncertain significance.</p><p>THE EXTRAXIAL SKELETON: AMBITAL FRAMEWORK</p><p>Because many ambiguities surround use of the term “marginal” among echinoderms (e.g., Mooi &amp; David 2000, 2008; Dean Shackleton 2005; Hotchkiss 2012; Blake 2013, 2018), the descriptive term “ambital framework” was proposed as a non-genetic supplement for use if homology is unclear (Blake 2013: 357; 2018: 7; 2024: 4; Blake &amp; Guensburg 2015: 479).</p><p>An ambital framework inferomarginal series is recognized in all somasteroid genera (Blake &amp; Hotchkiss 2022, contra Hunter &amp; Ortega-Hernández 2021), and except for D. spenceri n. gen., n. sp., all genera of the basal Euaxosida . Series expression among somasteroids has been argued as illustrating a general evolutionary sequencing toward greater clarity of definition (Blake 2013; Blake &amp; Lefebvre 2025). Given presence in ancestral somasteroids, absence of a marginal series from derivative Degeneraster n. gen. is considered a phylogenetic loss supporting familial recognition.</p><p>The much-varied robusticities of marginal ossicles found among asteroids (e.g., Figs 4A, C, F-H;5A-H) correlate at least in part with arm shape rather than phylogenetic positioning, more robust in taxa with flat arms, more weakly differentiated in taxa with cylindrical arms (Spencer 1922: 202; Blake &amp; Rozhnov 2007: 526).</p><p>THE EXTRAXIAL SKELETON: AXILLARY / ODONTOPHORE</p><p>The term“axillary”,typical of Paleozoic usage,and “odontophore”, typical of post-Paleozoic crown group usage, are synonyms (Spencer 1916: 62). An axillary has not been recognized among somasteroids (Blake &amp; Lefebvre 2025). The axillary has been widely considered a derivative of the inferomarginal series (e.g., Schuchert 1915: 14, under “interbrachial”; Spencer &amp; Wright 1966:14).The varied interbrachial expressions of a single specimen of Aerliceaster Blake, Gahn &amp; Guensburg, 2020b, suggest that the axillary is a part of the ambital framework and that axillary differentiation was emergent among early Asteroidea (Fig. 5B). Although some ossicular debris is developed distal to the MAO of D. spenceri n. gen., n. sp. (e.g., Fig. 2 B-D), potential axillary presence cannot be established or rejected based on available specimens.</p><p>THE EXTRAXIAL SKELETON: ACTINALS</p><p>Because of morphological differences, and because no intermediate state has been recognized, “actinals” of asteroids are considered phylogenetically independent of somasteroid virgalia, the adaxial virgals lost before actinals emerged (Blake 2013, 2018, 2024; Blake &amp; Lefebvre 2025). Actinals of most euaxosidans are irregular in form and arrangement (e.g., Figs 1F; 2B; 5B, C) arguing derivation as a space-filling device with distribution among taxa favoring homoplasy. Unlike somasteroid virgals, actinals are extraxial. Actinals are abundant in some early asteroids (e.g., Fig. 5C), in time and among lineages becoming more uniform in appearance and arrangement, including alignment into one or two clearly defined series (e.g., Hotchkiss &amp; Clark 1976; Blake &amp; Hotchkiss 2004; Blake et al. 2015b: 1049).</p><p>Among most asteroids, the ambital framework/marginal series separates abactinals from actinals, thereby providing an interpretive device unavailable for D. spenceri n. gen., n. sp. An ambital framework also is lacking from most ophiuroids, the aboral disk ossicles commonly extending without interruption around the disk edge to the oral surface. The ophiuran configuration has been interpreted as representing “downgrowths of the apical interradii” (Spencer 1919: 178, also 181; 1927: 367), a disposition endorsed by Dean Shackleton (2005: 42) and Gladwell (2018: 6). Arm ossicles adjacent to the adaxials of D. spenceri n. gen., n. sp. appear granular and those near the mouth frame are wide, flat, and plate-like (Figs 1; 2, esp. 2B, D), both unlike aboral abactinals (Fig. 1 A-E). Although a marginal series is lacking, the ossicular differentiation of D. spenceri n. gen., n. sp. suggests actinal differentiation rather than ophiuran “downgrowth”. Abactinal and actinal series differentiation in D. spenceri n. gen., n. sp. is consistent with evolutionary skeletal ambital framework loss, and yet a loss with retention of the boundary between ossicular series.</p><p>THE EXTRAXIAL SKELETON: ACCESSORIES</p><p>Accessories of somasteroids and more basal asteroids are predominantly small and little differentiated. Few accessories can be recognized on any of the three D. spenceri n. gen., n. sp. specimens, probably largely because of taphonomic loss. A prominent adaxial spine base, however, is recognized (e.g., Fig. 2D), and a possible row of attachment sites for small spinelets along MAO edges (Fig. 2C).</p></div>	https://treatment.plazi.org/id/CC63253534526E43FEABE771FB02F9E0	Public Domain	No known copyright restrictions apply. See Agosti, D., Egloff, W., 2009. Taxonomic information exchange and copyright: the Plazi approach. BMC Research Notes 2009, 2:53 for further explanation.		Plazi	Blake, Daniel B.;Lefebvre, Bertrand	Blake, Daniel B., Lefebvre, Bertrand (2026): Degeneraster spenceri n. gen., n. sp. (Asteroidea; Ordovician) and interpretating the early history of the Asterozoa. Comptes Rendus Palevol 25 (10): 173-187, DOI: 10.5852/cr-palevol2026v25a10, URL: https://doi.org/10.5852/cr-palevol2026v25a10
