Revista de Biología Tropical, ISSN electrónico: 2215-2075 Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

Heart urchins from the depths: Corparva lyrida gen. et sp. nov.

(Palaeotropidae), and new records for the southwestern Atlantic Ocean

Jonathan N. Flores

Pablo E. Penchaszadeh

Martín I. Brogger

1. Laboratorio de Ecosistemas Costeros, Plataforma y Mar Profundo. Museo Argentino de Ciencias Naturales

“Bernardino Rivadavia” (CONICET), Av. Ángel Gallardo 470, C1405DJR, Buenos Aires, Argentina; jflores@macn.

gov.ar; pablopench@gmail.com

2. Laboratorio de Reproducción y Biología Integrativa de Invertebrados Marinos, Instituto de Biología de Organismos

Marinos (CONICET), Bvd. Brown 2915, U9120ACD, Puerto Madryn, Chubut, Argentina; brogger@cenpat-conicet.

gob.ar (*Correspondence).

Received 07-V-2020. Corrected 08-VIII-2020. Accepted 07-X-2020.

ABSTRACT

Introduction: Sea urchins in the order Spatangoida are the most diverse group of extant echinoids. Objective:

Describe a new genus and species of Spatangoida from abyssal depths, and add new records for known spe-

cies. Methods: Specimens were collected during several cruises at different areas of the southwestern Atlantic

Ocean (SWAO), among 37-55° S latitude at depths ranging from 55 to 3 000 m. We present morphological and

ultrastructure analyses. Results: Corparva lyrida gen. et sp. nov. (Palaeotropidae) is described from the Mar del

Plata Canyon on the Argentine continental slope (2 950 m depth), the first record of this family from Argentina.

Corparva gen. nov. differs in having an apical system semi-ethmolytic, and labrum reaching to rear part of

second adjacent ambulacral plate. We also report the northernmost distribution and deepest record for Brisaster

moseleyi (38° S latitude, 2 212 m depth), the northward extension of the distribution range of Tripylus excavatus

(39° S latitude, 74 m depth), and the first record of Abatus philippii and Abatus agassizii at the Burdwood Bank/

MPA Namuncurá. Conclusions: The present work brings novel and updated data about the diversity and distri-

bution of spatangoids from the SWAO, including the description of C. lyrida gen. et sp. nov., and new records

of species. This shows how much remains to be known about the diversity and distribution of heart urchins in

the SWAO, especially from the deep-sea.

Key words: Atelostomata; sea urchins; deep-sea; diversity; Argentina; MPA-N/BB.

Flores, J.N., Penchaszadeh, P.E., & Brogger, M.I. (2021).

Heart urchins from the depths: Corparva lyrida

gen. et sp. nov. (Palaeotropidae), and new records

for the southwestern Atlantic Ocean. Revista de

Biología Tropical, 69(S1), 14-34. DOI 10.15517/rbt.

v69iSuppl.1.46320

Commonly known as heart urchins, the

irregular echinoids of the order Spatangoida

L. Agassiz, 1840 are represented in the fossil

record since the lowermost Cretaceous (Ber-

riasian, c. 145 Mya) and today are the most

diverse group of extant echinoids (Villier,

Néraudeau, Clavel, Neumann & David, 2004;

Stockley, Smith, Littlewood, Lessios & Mack-

enzie-Dodds, 2005). Spatangoids are widely

distributed throughout the ocean, from shallow

waters to abyssal depths. Mostly spatangoids

have evolved an infaunal lifestyle burrowing

into the superficial layer of unconsolidated

muddy and sandy sediments; however, some

species living in the deep sea have adopt-

ed an epifaunal lifestyle (Mortensen, 1950;

Mortensen,1951; Mironov, 1978). Owing

to their ecological traits, heart urchins are

DOI 10.15517/rbt.v69iSuppl.1.46320

Revista de Biología Tropical, ISSN electrónico: 2215-2075, Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

considered important components of benthic

communities. Spatangoids are deposit-feeders,

they ingest a large amount of detritus from the

sediment and cause bioturbation due to their

locomotion and feeding mode (De Ridder, Jan-

goux & De Vos, 1987; Lohrer, Thrush, Hunt,

Hancock & Lundquist, 2005). Concerning their

reproductive aspects, spatangoids show broad-

casting or brooding spawning modes, and

indirect or direct developmental strategy, these

life-history traits affects particularly the early

larval dispersion and the distribution patterns

of species (Poulin & Féral, 1996, 1998).

The southwestern Atlantic Ocean (SWAO)

receives waters formed in remotes areas of the

world, generating one of the most energetic

oceanic regions of the world (Piola & Matano,

2001). Along the Argentine continental shelf,

the upper ocean is mainly dominated by the

Malvinas Current, a branch of the Antarctic

Circumpolar Current that flows offshore to

north, the Brazil Current, a branch of the

subtropical gyre that flows south along the

continental slope of South America, and by the

Brazil/Malvinas Confluence, the collision of

these two opposite currents near 38° S latitude

(Matano, Palma & Piola, 2010). Also, the deep

layers from the continental slope off Argentina

are characterized by a variety of water masses

with origin in deep and bottom waters from the

North Atlantic, South Pacific, and Antarctic

regions (Piola & Matano, 2001). According with

several authors, two biogeographic provinces

are recognized on the Argentine continental

shelf by the patterns of distribution of different

macroinvertebrates taxa: the Argentine Bio-

geographic Province (ABP), and the Magellan

Biogeographic Province (MBP) (Bernasconi,

1964; Bastida, Roux & Martínez, 1992; Doti,

Roccatagliata & López Gappa, 2014). The ABP

extends from 23° S (Cabo Frio, Brazil) to 43° S

(Península Valdés, Argentina), while the MBP

is present on both sides of South America, from

the southeastern Pacific Ocean at 41° S (Puerto

Montt, Chile) reaching around the tip of South

America into the SWAO at 43° S latitude,

where the MBP turns aside from shallow shelf

waters following a northeastern direction to

more deep shelf waters, as far as 35° S latitude

(López Gappa, Alonso & Landoni, 2006; Doti

et al., 2014).

Based on previous reports, there are eight

spatangoids species present in the Argentine

continental shelf and offshore: Abatus caver-

nosus (Philippi, 1845); Abatus philippii Lovén,

1871; Abatus agassizii Mortensen, 1910; Bri-

saster moseleyi (A. Agassiz, 1881); Tripylaster

philippii (Gray, 1851); Tripylus excavatus

(Philippi, 1845); Tripylus reductus (Koehler,

1912); and Delopatagus brucei Koehler, 1907

(Bernasconi, 1964; Brogger et al., 2013; Fabri-

Ruiz, Saucède, Danis & David, 2017; Saucède

et al., 2020). D. brucei is considered due

to its occurrence south off Tierra del Fuego

(Saucède et al., 2020).

This paper aims to contribute to improving

the knowledge of the diversity and distribution

of the Spatangoida from the SWAO, through

the study of specimens recently collected.

Here we describe a new genus and species of

Palaeotropidae from the Mar del Plata Canyon,

which represents the first report for this family

in Argentina. Besides, we inform new records

in the SWAO for other known species.

MATERIALS AND METHODS

The study area is located at the southern

extreme of the SWAO, from 37° to 55° S lati-

tude at depths encompassing from the shallow

waters of the continental shelf to abyssal waters

of the slope off the Argentine coast (Fig. 1A).

The specimens were collected from sev-

eral sites during eight cruises at different

areas within the SWAO: continental shelf and

slope off Buenos Aires, the Mar del Plata

Canyon, San Jorge Gulf, Patagonian shelf, and

the Marine Protected Area Namuncurá/Banco

Burdwood (MPA-N/BB). These cruises were:

“Mejillón II” (M II), 2009, 9-150 m depth,

3 sites; “Talud Continental I” (TC I), 2012,

200-3 006 m depth, 6 sites; “Talud Continental

II” (TC II), 2013, 78-1 289 m depth, 2 sites;

“Talud Continental III” (TC III), 2013, 1 310-3

447 m depth, 5 sites; “Área Marina Prote-

gida Namuncurá/Banco Burdwood: Bentos”

Revista de Biología Tropical, ISSN electrónico: 2215-2075 Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

Fig. 1. Maps showing the studied area with the distribution of the species discussed in the present study. A. Positions for the

main locations from the southwestern Atlantic Ocean discussed in this study. B. Corparva lyrida gen. et sp. nov. C. Tripylus

excavatus. D. Tripylus reductus. E. Abatus cavernosus. F. Abatus philippii. G. Abatus agassizii. H. Brisaster moseleyi. I.

Tripylaster philippii. B–I. species herein examined (marked signs) plotted on their previously registered distribution (dotted

area). References: A. SWAO, southwestern Atlantic Ocean; mdp, Mar del Plata Canyon; mi, Malvinas Islands; bb, Marine

Protected Area Namuncurá/Banco Burdwood; tdf, Tierra del Fuego; sg, South Georgia Islands; so, South Orkney Islands;

ss, South Shetland Islands; and ap, Antarctic Peninsula.

Revista de Biología Tropical, ISSN electrónico: 2215-2075, Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

(AMP-N/BB-2016), 2016, 71-785 m depth, 16

sites; “PD BB ABR 17” (AMP-N/BB-2017),

2017, 48-646 m depth, 9 sites, “Pampa Azul

Golfo San Jorge–BO/PD-GSJ-02-2017” (GSJ

2017), 2017, 36-106 m depth, 19 sites, and

“AMP Namuncurá/Banco Burdwood: Ingenie-

ros Ecosistémicos” (AMP-N/BB-2018), 2018,

78–694 m depth, 2 sites (Table 1). All cruises

were performed on board of the R/V Puerto

Deseado from CONICET.

Specimens were collected using an adapt-

ed towed dredge or a bottom trawl net. The

towed dredge used consisted of a rigid body

structure 150 cm long and 100 cm wide, with

a 60 cm wide by 40 cm high mouth frame and

carrying two joint fishing nets with two differ-

ent pore-size (an external one of 3x3 cm, with

another internal one of 1x1 cm).

Once onboard, specimens were fixed in 96

% ethanol. All the specimens are now housed

TABLE 1

Collection data of the specimens studied

MACN-In Expedition - Station - Site Lat. (S) Long. (W) Depth (m) Date (yy-mm-dd) Spms. Fishing gear

43269 M II - 7 38°46’34” 55°50’38” 92 2009-09-11 1 towed dredge

43270

M II - 10

39°05’49” 58°02’09” 74 2009-09-12 3 towed dredge

43271

M II - 11

39°01’23” 58°10’02” 55 2009-09-12 3 towed dredge

43272

TC I - 2

37°57’11” 55°11’03” 291 2012-08-10 1 towed dredge

43273 TC I - 3 37°59’39” 55°13’03” 250 2012-08-10 16 bottom trawl net

43274

TC I - 5

37°58’39” 55°09’06” 528 2012-08-10 1 bottom traw1 net

43275 TC I - 14 38°00’59” 54°30’19” 1 006 2012-08-11 2 bottom trawl net

43276 TC I - 32 37°59’48” 55°12’29” 319 2012-08-17 1 towed dredge

43277 TC I - 33 37°58’42” 55°11’54” 308 2012-08-17 2 bottom trawl net

43278 TC II - 43 37°53’50” 54°30’27’’ 998 2013-05-26 1 bottom traw1 net

43279 TC II - 44 37°53’33” 54°42’56” 780 2013-05-26 3 bottom trawl net

43280 TC III - 47 38°06’34” 53°42’50” 2 950 2013-09-06 1 bottom trawl net

43281 TC III - 51 38°01’23” 53°51’00” 2 212 2013-09-07 1 bottom traw1 net

43282 TC III - 53 37°52’37” 53°54’15” 1 763 2013-09-08 12 bottom trawl net

43283 TC III - 55 37°52’09” 53°51’35” 1 712 2013-09-08 9 bottom trawl net

43284 TC III - 59 37°49’41” 54°5’14” 1 398 2013-09-10 1 bottom trawl net

43285 AMP-N/BB-2016 - 5 - 126 55°02’17” 65°46’07’’ 118 2016-04-06 1 towed dredge

43286 AMP-N/BB-2016 - 5 - 127 55°02’15” 65°48’24” 114 2016-04-06 1 bottom traw1 net

43287 AMP-N/BB-2016 - 11 - 338 54°30’06” 64°12’06” 107 2016-04-22 1 bottom trawl net

43288 AMP-N/BB-2016 - 23 - 226 54°45’34” 59°52’08” 182 2016-04-13 1 bottom trawl net

43289 AMP-N/BB-2016 - 26 - 24 54°24’13” 58°28’17” 135 2016-03-29 1 towed dredge

43290 AMP-N/BB-2016 - 26 - 27 54°24’57” 58°30’55” 137 2016-03-29 1 bottom trawl net

43291 AMP-N/BB-2016 - 28 - 50 54°28’50” 59°11’40” 122 2016-03-30 1 towed dredge

43292 AMP-N/BB-2016 - 30 - 185 54°16’40” 59°57’47” 96 2016-04-10 1 towed dredge

43293 AMP-N/BB-2016 - 31 - 197 54°29’58” 59°51’32” 109 2016-04-10 3 bottom trawl net

43294 AMP-N/BB-2016 - 32 - 77 54°32’36” 60°01’17” 98 2016-03-30 1 bottom traw1 net

43295 AMP-N/BB-2016 - 33 - 159 54°25’46” 60°38’52” 101 2016-04-08 5 bottom trawl net

43296 AMP-N/BB-2016 - 34 - 156 54°27’15” 60°58’49” 100 2016-04-07 15 bottom trawl net

43297 AMP-N/BB-2016 - 39 - 141 54°50’41” 63°59’54” 183 2016-04-06 1 bottom traw1 net

43298 AMP-N/BB-2016 - 39 - 141 54°50’41” 63°59’54” 183 2016-04-06 2 bottom trawl net

43299 AMP-N/BB-2016 - 41 - 350 54°19’55” 64°14’15” 122 2016-04-22 1 bottom trawl net

43300 AMP-N/BB-2016 - 41 - 350 54°19’55” 64°14’15” 122 2016-04-22 5 bottom trawl net

43301 AMP-N/BB-2017 - 5- 10 53°07’41” 65°47’08” 294 2017-04-23 2 towed dredge

43302 AMP-N/BB-2017 - 9 - 49 54°52’34” 64°17’46” 146 2017-04-24 1 towed dredge

Revista de Biología Tropical, ISSN electrónico: 2215-2075 Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

in the National Invertebrate Collection of the

Museo Argentino de Ciencias Naturales “Ber-

nardino Rivadavia” (MACN-In) from Buenos

Aires, Argentina.

Gross morphology of specimens was stud-

ied under naked eye and using a stereomi-

croscope, while the ultrastructure of several

appendages was analyzed by scanning electron

microscopy (SEM). Test measures were made

with a digital caliper. To be able to reveal

the arrangement of the plates, some speci-

mens were carefully cleaned. Appendages and

soft tissue were removed from the test with

tweezers, and a small brush soaked with a

diluted solution of sodium hypochlorite was

used to remove the organic remains. When the

plates and sutures were exposed and visible, the

whole specimen was rinsed in distilled water.

Plates were labelled according to the standard

nomenclature for the test plating provided by

Lovén (1874).

For SEM images, appendages (spines,

pedicellariae, sphaeridia, and tube feet) were

removed from different parts of the test and

placed into distilled water. Organic remains

were cleared with a diluted solution of sodium

TABLE 1 (Continued)

MACN-In Expedition - Station - Site Lat. (S) Long. (W) Depth (m) Date (yy-mm-dd) Spms. Fishing gear

43303 AMP-N/BB-2017 - 23 - 173 54°26’06” 59°30’15” 91 2017-05-01 1 bottom trawl net

43304 AMP-N/BB-2017 - 24 - 184 54°19’57” 59°53’45” 97 2017-05-01 1 bottom traw1 net

43305 AMP-N/BB-2017 - 25 - 304 54°20’46” 60°20’46” 104 2017-05-09 1 bottom trawl net

43306 AMP-N/BB-2017 - 27 - 326 54°06’27” 60°52’46” 128 2017-05-09 1 bottom trawl net

43307 AMP-N/BB-2017 - 27 - 326 54°06’27” 60°52’46” 128 2017-05-09 1 bottom trawl net

43308 AMP-N/BB-2017 - 27 - 327 54°06’27” 60°52’46” 132 2017-05-09 2 towed dredge

43309 AMP-N/BB-2017 - 31 - 269 53°40’21” 61°38’15” 642 2017-05-07 38 bottom traw1 net

43310 GSJ 2017 - 3 - ID 55 43°43’12” 64°31’48” 65 2017-10-29 1 bottom trawl net

43311 GSJ 2017 - 11 - ID 42 44°53’24” 65°08’24” 84 2017-10-31 4 bottom trawl net

43312 GSJ 2017 -12 - ID 41 45°08’24” 64°50’60” 83 2017-10-31 1 bottom traw1 net

43313 GSJ 2017 - 13 - ID 39 45°14’24” 65°09’00” 91 2017-10-31 1 bottom trawl net

43314 GSJ 2017 - 17 - ID 36 45°13’12 “ 66°13’48” 78 2017-11-01 1 bottom trawl net

43315 GSJ 2017 - 23 - ID 32 45°34’48” 66°11’24” 94 2017-11-02 38 bottom trawl net

43316 GSJ 2017 - 24 - ID 31 45°32’24” 65°48 ‘36” 98 2017-11-02 2 bottom trawl net

43317 GSJ 2017 - 26 - ID 29 45°34’48” 66°07’48” 83 2017-11-02 1 bottom traw1 net

43318 GSJ 2017 - 29 - ID 26 45°55’12” 65°50’24” 99 2017-11-03 1 bottom trawl net

43319 GSJ 2017 - 31 - ID 24 45°53’60” 66°35’24” 96 2017-11-03 47 bottom traw1 net

43320 GSJ 2017 - 33 - ID 22 45°54’36” 67°18’36” 72 2017-11-03 1 bottom trawl net

43321 GSJ 2017 - 37 - ID 19 46°13’48” 66°33’36” 99 2017-11-04 4 bottom trawl net

43322 GSJ 2017 - 39 - ID 17 46°14’24” 65°49’12” 98 2017-11-04 26 bottom trawl net

43323 GSJ 2017 - 42 - ID 14 46°34’48” 65°08’24” 106 2017-11-05 1 bottom trawl net

43324 GSJ 2017 - 42 - ID 14 46°34’48” 65°08’24” 106 2017-11-05 1 bottom traw1 net

43325 GSJ 2017 - 54 - ID 68 46°54’36” 66°42’36” 57 2017-11-06 1 bottom trawl net

43326 GSJ 2017 - 55 - ID 69 46°45’36” 66°54’36” 74 2017-11-07 1 bottom trawl net

43327 GSJ 2017 - 56 - ID 8 46°32’24” 67°19’48” 74 2017-11-07 5 bottom traw1 net

43328 GSJ 2017 - 59 - ID 10 46°33’36” 66°36’36” 95 2017-11-07 11 bottom trawl net

43329 AMP-N/BB-2018 - 1 - 157 54°53’00” 67°48’36” 140 2018-09-01 3 bottom trawl net

43330 AMP-N/BB-2018 - 25- 120 54°30’48” 60°25’35” 100 2018-08-28 1 bottom trawl net

References: M II “Mejillon II” expedition; TC I “Talud Continental I” expedition; TC II “Talud Continental II” expedition;

TC III “Talud Continental III” expedition; AMP-N/BB-2016 “Area Marina Protegida Namuncurá - Banco Burdwood”

expedition; AMP-N/BB-2017 “PD BB ABR 17” expedition; AMP-N/BB-2018 “AMP Namuncurá/Banco Burdwood:

Ingenieros Ecosistémicos” expedition; GSJ 2017 “Pampa Azul Golfo San Jorge–BO/PD-GSJ-02-2017” expedition; and

Spms. number of specimens.

Revista de Biología Tropical, ISSN electrónico: 2215-2075, Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

hypochlorite for a few minutes. The append-

ages were rinsed in distilled water twice, fol-

lowed by a third rinse with 96 % ethanol to

allow rapid air drying. Finally, appendages

were transferred to aluminium stubs, sputtered

with gold-palladium, and examined and photo-

graphed with a Philips XL30 scanning micro-

scope at the Museo Argentino de Ciencias

Naturales “Bernardino Rivadavia” (MACN).

Complete specimens were photographed using

a Nikon D800 camera with a Micro-Nikkor 60

mm f/2.8 lens, and details of the plates from the

test were photographed with a Zeiss Discovery

V20 stereoscopic microscope.

This article is registered in ZooBank under

ID: urn:lsid:zoobank.org:pub:2FBDDA8F-

DB8A-4266-B606-553AF5C2F366.

RESULTS

In all, 299 specimens of spatangoids were

collected and studied, identifying eight species

distributed in two families, and six genera. In

the present study, we report a new genus and

species Corparva lyrida (Spatangoida: Pala-

etropidae) along with the occurrence and new

records in the SWAO of known species.

In the Taxonomic List are listed the spe-

cies identified following the classification of

Kroh (2020) for higher-level taxa, Saucède et

al. (2020) for the family Schizasteridae and its

lower-level taxa, and Kroh & Mooi (2020) for

the Palaeotropidae family.

Taxonomic List:

Phylum Echinodermata Bruguière, 1791

Class Echinoidea Leske, 1778

Order Spatangoida L. Agassiz, 1840

Suborder Paleopneustina Markov & Solovjev,

2001

Family Schizasteridae Lambert, 1905

Genus Tripylus Philippi, 1845

Tripylus excavatus (Philippi, 1845)

Tripylus reductus (Koehler, 1912)

Genus Abatus Troschel, 1851

Abatus cavernosus (Philippi, 1845)

Abatus philippii Lovén, 1871

Abatus agassizii Mortensen, 1910

Genus Brisaster Gray, 1855

Brisaster moseleyi (A. Agassiz, 1881)

Genus Tripylaster Mortensen, 1907

Tripylaster philippii (Gray, 1851)

Suborder Brissidina Kroh & Smith, 2010 (=

Brissidea of Stockley et al., 2005)

Family Palaeotropidae Lambert, 1896

Genus Corparva Flores, Penchaszadeh &

Brogger gen. nov.

Corparva lyrida Flores, Penchaszadeh &

Brogger sp. nov.

Systematics:

Order Spatangoida L. Agassiz, 1840

Suborder Brissidina Kroh & Smith, 2010

Family Palaeotropidae Lambert, 1896

Corparva Flores, Penchaszadeh & Brogger

gen. nov.

Diagnosis: Test ovoid, small size, trun-

cated posterior end. Semi-ethmolytic apical

system, four gonopores. No frontal notch.

Paired ambulacra apetaloid, pore-pairs small

and rudimentary. Fascioles absent. Periproct on

the posterior end, slightly inframarginal. Peri-

stome D-shaped, sunken. Labrum narrow, not

projecting over the peristome, reaching to rear

part of second adjacent ambulacral plate. Plas-

tron amphisternous, domed in profile. Primary

spines slender, more abundant on aboral side,

lacking on posterior ambulacral areas on oral

side. Pedicellariae present: tridentate, globifer-

ous, and triphyllous.

Type species: Corparva lyrida Flores, Pen-

chaszadeh & Brogger sp. nov.

Etymology: Cor alluding for heart and

parva for small (gender feminine).

ZooBank ID: urn:lsid:zoobank.

org:act:13ACEDA6-DA67-414A-BBEE-

9FB20288223F

Remarks: Corparva gen. nov. is included

into the family Palaeotropidae Lambert, 1896

based on structural features as a thin ovate test,

no frontal notch, paired ambulacra apetaloid,

reduced peristome D-shaped, sternal plates

symmetrical and fully tuberculate, episternal

plates paired, and aboral surface with scattered

small tubercles (Smith & Gale, 2009; Smith

Revista de Biología Tropical, ISSN electrónico: 2215-2075 Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

& Kroh, 2011). However, Corparva gen. nov.

can be clearly separated from other genera of

Palaeotropidae by possessing an apical system

semi-ethmolytic, labral plate reaching to rear

part of second adjacent ambulacral plate, and

paired ambulacra deeply depressed forming

rounded pouches (at least in females). We con-

sidered these features serve to distinguish our

new species C. lyrida supporting the erection

of a new genus.

As Néraudeau, David & Madon (1998)

pointed out, the arrangement of the plates in

the apical system should not be used as a mor-

phological character to differentiate at family

level, due to changes in the structure of the

apical system occurred convergently in many

different groups of spatangoids. Thus, we con-

sider the semi-ethmolytic pattern of Corparva

gen. nov. and the labral plate extending to the

rear part of second adjacent ambulacral plate

as features to separates it from the other genera

of Palaeotropidae.

Palaeotropus Lovén, 1874 differs by pos-

sessing an apical system monobasal with fused

genital plates, anterior, two gonopores, paired

ambulacra flush, uniserial ambulacral plates

adapically, labral plate extending to rear of the

first adjacent ambulacral plate, episternal plates

strongly tapered to posterior, strong subanal

heel, rounded subanal fasciole, row of larg-

er tubercles and spines bordering the frontal

ambulacrum, and ophicephalus pedicellariae

present (Lóven, 1871; Lóven, 1874; Mortensen,

1950; Mironov, 2006; Kroh & Mooi, 2020).

Palaeobrissus A. Agassiz, 1883 differs by

its ethmolytic apical system with fused genital

plates, anterior, two gonopores in the posterior

genital plates surrounded by a rim and some-

times two smaller anterior gonopores in large

specimens, paired ambulacra flush, subpetaloid

with ambulacral pores double, peristome not

sunken and transversally oval, labral plate

extending to first adjacent ambulacral plate,

slightly projecting over peristome, and rounded

subanal fasciole present in juveniles (lost in

adults) (Agassiz, 1883; Mortensen; 1950; Kroh

& Mooi, 2020).

Paleotrema Koehler, 1914 differs by hav-

ing a test elongated, posterior end obliquely

truncated, monobasal apical system with fused

genital plates, anterior, three gonopores, paired

ambulacra flush, labral plate extending to first

adjacent ambulacral plate, episternal plates

strongly tapered to posterior, plastron form-

ing keel posteriorly, rounded subanal fasciole,

row of larger tubercles and spines bordering

the frontal ambulacrum, ophicephalus pedicel-

lariae present and globiferous absent (Agassiz,

1879; Koehler, 1914; Mortensen, 1950; Kroh

& Mooi, 2020).

Scrippsechinus Allison, Durham & Mintz,

1967 differs by possessing ethmolytic apical

system with fused genital plates, subcentral,

paired ambulacra flush, uniserial ambulacral

plates adapically, labral plate not extending

beyond first adjacent ambulacral plate, project-

ing over peristome, and globiferous pedicel-

lariae absent (Allison, Durham & Mintz, 1967;

Kroh & Mooi, 2020).

Kermabrissoides Baker, 1998 differs by

its ethmolytic apical system, subcentral, gono-

pores on top of small cones, paired ambulacra

flush, subpetaloid, labral plate extending to

third adjacent ambulacral plate, rounded sub-

anal fasciole with 2-3 tube feet either side,

ophicephalus pedicellariae present and glo-

biferous absent (Baker & Rowe, 1990; Baker,

1998; Kroh & Mooi, 2020).

Corparva lyrida

Flores, Penchaszadeh & Brogger sp. nov.

Diagnosis: As for the genus.

Description: Test fragile, low in profile,

oval in outline with truncated posterior end,

anterior part wider than posterior part, rounded

at ambital edge, wedge-shaped in lateral profile

(Fig. 2A, Fig. 2B, Fig. 2C, Fig. 2D, Fig. 2E,

Fig. 3A, Fig. 3B, Fig. 3C, Fig. 3D, Fig. 3E).

Small test size, 18.2 mm long, 14.8 mm wide,

and 6.0 mm high. Fascioles absent (Fig. 2A,

Fig. 2B, Fig. 2C, Fig. 2D, Fig. 2E, Fig. 3A,

Fig. 3B, Fig. 3C, Fig. 3D, Fig. 3E). Apical

system central, sunken with respect to adjacent

interambulacral areas, semi-ethmolytic, with

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four genital pores of same size opening on

inner part of genitals (Fig. 2A, Fig. 3A, Fig.

4A, Fig. 4D). Madreporic plate (G2) enlarged

posteriorly between genitals 1 and 4 but not

separating oculars V from I, hydropores scarce

(Fig. 4D). Frontal notch absent, ambulacrum

III flush with test (Fig. 2A, Fig. 2D, Fig.

3A, Fig. 3D). Non-petaloid paired ambulacra,

cruciform, deeply depressed forming rounded

pouches (Fig 3A), double row of ambulacral

plates adapically. Ambulacral tube feet simple

on aboral side, pore-pairs small and rudimen-

tary, there are no occluded plates at the end of

the paired ambulacra, posterior paired ambula-

cra slightly shorter than anterior. Paired ambu-

lacra pouches reaching fifth ambulacral plate

(from apex to ambitus) in ambulacrum IV and

V, tuberculation on these plates scarce. Plates

from ambulacra II and IV remain parallel-sided

on oral side (Fig 3B). Peristome D-shaped,

sunken, situated between 25-34% of test length

from anterior edge, upper peristome portion

occupied by many plates of different sizes,

becoming smaller surrounding mouth (Fig. 3B,

Fig. 4C, Fig. 4F). Phyllodes reaching fourth

plate in paired ambulacra. Penicillate tube feet

Fig. 2. Corparva lyrida gen. et sp. nov. (Holotype MACN-In 43280), complete specimen. A. Aboral view. B. Oral view. C.

Posterior view. D. Anterior view. E. Side view (anterior to the left).

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conspicuous (Fig. 2B, Fig. 3B), terminating in

well-developed disc with finger-like projec-

tions, each supported by a skeletal rod (Fig.

5G). Interambulacrum 5 continuous, posterior

part forming slightly keel (Fig. 2E, Fig. 3E).

Labral plate not projecting over peristome, nar-

row, in contact with both sternal plates, extend-

ing to rear part of second adjacent ambulacral

plate (Fig. 4C, Fig. 4F). Plastron amphisternous

(Fig. 4F). Sternal plates symmetrical, slightly

bowed, extending to fifth adjacent ambulacral

plate, posterior suture of plate 5.b.2 coincides

with fifth plate in ambulacrum I (Fig. 4F). Epi-

sternal plates paired and opposite. Basicoronal

plate amphiplacous in interambulacrum 4. Peri-

proct circular, located on posterior vertical end,

inframarginal, visible from oral side, covered

by plates of variable sizes and shapes, larger

plates close to external edge and smaller plates

towards center (Fig. 2B, Fig. 2C, Fig. 3B, Fig.

3C). Distinct subanal tube feet absent. Primary

tubercles numerous and uniformly spaced on

aboral surface and absent on ambulacral areas

on oral side up to fifth plate in ambulacrum

Fig. 3. Corparva lyrida gen. et sp. nov. (Holotype MACN-In 43280), specimen partially cleaned. A. Aboral view. B. Oral

view. C. Posterior view. D. Anterior view. E. Side view (anterior to the left).

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V and fourth plate in ambulacrum I (Fig. 2B,

Fig. 3B), mamelon well-developed with central

perforation and slightly crenulated base, areole

well-developed (Fig. 4B, Fig. 4E). Secondary

tubercles smaller, with same general shape as

primary ones, with mamelon usually reduced.

Spines scattered on oral side of ambulacra

I and V, but uniformly distributed in sternal

plates, ambital region, and apical side (Fig.

2A, Fig. 2B). Primary spines shorter, straight,

with pointed tip, and shaft with longitudinal

and ornamented striations (Fig. 5D). Longest

primary spines found on plastron. They are

large, curved and spatulate towards distal end,

with well-developed acetabulum and base,

poorly developed milled ring, and shaft with

longitudinal smooth striations (Fig. 5A, Fig.

5B, Fig. 5C). Spine cylinder with helicoidal

pore arrangement (Fig. 5E). Globiferous, tri-

dentate, and triphyllous pedicellariae (Fig. 5H,

Fig. 4. Morphological details and drawings of Corparva lyrida gen. et sp. nov. A. Apical system. B. Primary tubercle.

C. Peristome. D. Hemilytic (semi-ethmolytic) apical system plating drawing. E. Primary tubercle diagram. F. Peristome

and plastron plating drawing. References: D. 1–4 genital plates (2 also madreporite), and I–V ocular plates; E. a areole, c

crenulated platform, and m perforated mamelon; and F. p peristome, L labrum, S

sternal plates, I and V ambulacra, and 5

posterior interambulacrum.

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Fig. 5I, Fig. 5J, Fig. 5K, Fig. 5L). Globiferous

pedicellariae more frequently found on apical

side, head and stalk embedded in a yellowish

tissue, three-valved, valves whit large and wide

base, blade forms a curved semi-tube terminat-

ing in 3-6 sharp and tiny hooks (Fig. 5H, Fig.

5I). Tridentate pedicellariae on apical and oral

side, three-valved, shovel-shaped valves with

widen and finely serrated distal part separated

from triangular base by elongated, narrow, and

straight tubular part (Fig. 5J, Fig. 5K). Triphyl-

lous pedicellariae smallest, with minute base,

and large and wide blade with finely serrated

edge (Fig. 5L). Sphaeridiae swollen in shape,

irregularly rugose (Fig. 5F), on short stalks,

numerous along posterior ambulacral areas

on oral side. Test colour brown-brownish with

whitish spines in ethanol; denuded test white.

Etymology: lyrida refers to the April

Lyrids, the meteor shower that occurs each year

Fig. 5. SEM images of appendages of Corparva lyrida gen. et sp. nov. A-C. Primary spines from the plastron. D.

Ambulacrum spine from the oral side. E. View of the inner cylinder of a primary spine. F. Spheridium. G. Skeletal rod from

an oral penicillate podium. H-I. Valve of globiferous pedicellaria with three and four terminal teeth, respectively. J. Valve

of a tridentate pedicellaria. K. Tridentate pedicellaria. L. Valve of a triphyllous pedicellaria.

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in the constellation Lyra. The specific name is a

noun in apposition (feminine).

Examined material: Holotype MACN-In

43280 (one half denuded specimen in ethanol

70 %, and external appendages mounted on

three SEM stubs) (Table 1).

Type locality: Mar del Plata Canyon

(38°06’34’’ S & 53°42’50’’ W), Argentine con-

tinental slope (Fig. 1B).

Depth: 2 950 m.

Distribution: Only know from the type

locality (Fig. 1B).

Zoobank ID: urn:lsid:zoobank.

org:act:9B936F7D-860D-4138-A991-

673821C3AF48

Remarks: C. lyrida sp. nov. is based on a

single complete specimen (holotype MACN-In

43280). Its test is fragile and small (18.2 mm

long, 14.8 mm wide, and 6.0 mm high), despite

this we consider that the specimen studied is an

adult, due to the presence of open gonopores.

Of course, this supposition is not conclusive

but it is in accordance with the characteristic

small form of adult specimens among the

family Palaeotropidae (Lovén 1871; Koehler,

1914; Mortensen, 1950; Allison, Duncan &

Mintz, 1967; Baker & Rowe, 1990; Mironov,

2006). Mortensen (1950) report the presence

of mature gonads containing a few ripe eggs

in a specimen of Palaeotropus josephinae of

14 mm length.

In some spatangoids, fascioles may be

present during all stage of development, in

others they are present in juveniles and then

maybe secondarily lost in adults, and in some

taxa there is no evidence that fascioles were

developed during ontogeny (Smith & Stockley,

2005; Stockley et al., 2005). Due to the holo-

type of C. lyrida sp. nov. does not present any

trace of fascioles, and it is the only specimen

that we have, we assumed that fascioles are

absent at least in adults. Additional specimens

in different stages of development are needed

to test if fascioles develop during ontogeny or

it is completely lost in C. lyrida sp. nov.

Corparva lyrida sp. nov. shows various

secondary morphological simplifications that

suggest an epibenthic lifestyle. As is observed

in many others deep-sea spatangoids (Larrain,

1985; Stockley et al. 2005; Saitoh & Kanazawa,

2012), C. lyrida sp. nov. has features related

with the building and maintenance of sanitary

funnels poorly developed (absence of fascioles

and distinctive tufts of spines on the aboral

side or at the posterior end of the test, and the

inframarginal position of the anus). Besides,

others ecological traits present in deep-sea taxa

and C. lyrida are the test thinner than shallow

waters spatangoids, and the poorly developed

(or completely lost in some groups) of petals

and specialized tube feet, due to in the deep-sea

the respiratory demanding is less than in shal-

low waters (Stockley et al., 2005).

Family Schizasteridae Lambert, 1905

Genus Tripylus Philippi, 1845

Tripylus excavatus (Philippi, 1845)

(Fig. 6A)

Examined material: MACN-In 43270

(Table 1).

Distribution: Tripylus excavatus occurs

northward in the SWAO at 39° S (this study),

and southward occurs along the Strait of

Magellan, Tierra del Fuego, Isla de los Estados,

and Cape Horn (Fig. 1C) (Fabri-Ruiz et al.,

2017). Also recorded at South Georgia Islands

(Saucède et al., 2020).

Depth: From the littoral to 110 m depth

(Saucède et al., 2020).

Remarks: Here we report the northern-

most record for T. excavatus at 39°05’49’’ S

& 58°02’09’’ W at 74 m depth (Table 1, Fig.

1C), resulting in a great extension in its range

of distribution. Despite its broad wide range,

T. excavatus seems to be an unusual species.

Among 299 spatangoids collected we found

only three specimens, this peculiarity also was

highlighted by Bernasconi (1953, 1966). In this

line, is to be expected that the disjunct distribu-

tion shown in figure 1C became continuous as

the sampling increasing in both effort and qual-

ity for this area.

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Tripylus reductus (Koehler, 1912)

Examined material: MACN-In 43285,

MACN-In 43286, MACN-In 43297, MACN-

In 43299 (Table 1).

Distribution: T. reductus is restricted to

the southern region of the SWAO (Tierra del

Fuego, Isla de los Estados) (Fig. 1D), and the

northern part of the Antarctic Peninsula, also

South Shetland Islands, and South Orkney

Islands (Saucède et al., 2020).

Depth: From 50 to 761 m depth (Saucède

et al., 2020).

Tripylus sp.

Examined material: MACN-In 43302

(Table 1).

Fig. 6. Images of specimens discussed in the present study. A. Aboral view of Tripylus excavatus (Philippi, 1845) (MACN-

In 43270, specimen partially cleaned). B. Aboral view of Abatus cavernosus (Philippi, 1845) (MACN-In 43314). C. Aboral

view of Abatus philippii Lovén, 1871 (MACN-In 43273). D. Aboral view of Abatus agassizii Mortensen, 1910 (MACN-In

43304). E. Aboral view of Brisaster moseleyi (A. Agassiz, 1881) (MACN-In 43309), specimen partially cleaned). F. Aboral

view of Tripylaster philippii (Gray, 1851) (MACN-In 43316).

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Distribution: Isla de los Estados.

Depth: 146 m.

Remarks: Test fragment identified at the

generic level due to the lack of diagnostic

characters.

Genus Abatus Troschel, 1851

Abatus cavernosus (Philippi, 1845)

(Fig. 6B)

Examined material: MACN-In 43314

(Table 1).

Distribution: Wide distribution along the

SWAO from 35° S to 55° S, including the Straits

of Magellan, and Malvinas Islands (Fig. 1E)

(Brogger et al., 2013). Also, along the Antarctic

Peninsula, South Orkney Islands, South Geor-

gia Islands, South Shetland Islands, and Bouvet

Islands (David, Saucède, Chenuil, Steimetz &

De Ridder, 2016; Saucède et al., 2020).

Depth: From 10 to 1 000 m depth (Saucède

et al., 2020). Abatus cavernosus is commonly

found in shallow waters southward of 44° S,

while northward off Buenos Aires it occurs

from 100 to 1 000 m depth (Brogger et al.,

2013; Saucède et al., 2020).

Abatus philippii Lovén, 1871

(Fig. 6C)

Examined material: MACN-In 43269,

MACN-In 43272, MACN-In 43273, MACN-

In 43276, MACN-In 43277, MACN-In 43287,

MACN-In 43288, MACN-In 43290, MACN-In

43291, MACN-In 43292, MACN-In 43294,

MACN-In 43295, MACN-In 43298, MACN-

In 43301, MACN-In 43305, MACN-In 43306,

MACN-In 43308, MACN-In 43323 (Table 1).

Distribution: Widely distributed along the

SWAO from 35° S to 55° S, including the Strait

of Magellan, Isla de los Estados, Malvinas

Islands (Bernasconi, 1964; Bernasconi,1966;

Fabri-Ruiz et al., 2017), and the MPA-N/BB

(this study). In the southeastern Pacific Ocean

at 52° S latitude. In the Southern Ocean record-

ed at South Georgia Islands, South Shetland

Islands, South Orkney Island, Sabrina Coast,

and Ross Sea (Saucède et al., 2020).

Depth: From 25 to 800 m depth (Saucède

et al., 2020).

Remarks: Here we report the first record

for A. philippi at the MPA-N/BB (Table 1). Due

to the occurrence of the species in surround-

ing areas, its presence in the AMP-N/BB was

expected (Fig. 1F).

Abatus agassizii Mortensen, 1910

(Fig. 6D)

Examined material: MACN-In 43293,

MACN-In 43296, MACN-In 43300, MACN-

In 43303, MACN-In 43304, MACN-In 43307

(Table 1).

Distribution: A. agassizii occurs in the

southern region of the SWAO, including Tierra

del Fuego, Isla de los Estados, Malvinas Islands

(Bernasconi, 1964; Saucéde et al., 2020), and

the AMP-N/BB (this study) (Fig. 1G). Also

recorded in the Southern Ocean at South Geor-

gia Islands, South Shetland Island, the northern

end of the Antarctic Peninsula, and in the east-

ern Weddell Sea (Saucède et al., 2020).

Depth: From the littoral to 600 m depth

(Saucède et al., 2020).

Remarks: Here we report the first record

for A. agassizii at the MPA-N/BB (Table). The

range of distribution known for A. agassizii

seems to have a north limit at Malvinas Islands.

These new records for the AMP-N/BB are in

accord with the distribution area known for the

species (Fig. 1G).

Abatus sp.

Examined material: MACN-In 43289,

MACN-In 43330 (Table 1).

Distribution: MPA-N/BB.

Depth: MACN-In 43289 at 135 m depth,

and MACN-In 43330 at 100 m depth

Remarks: Two test fragments identified at

the generic level due to the lack of diagnostic

characters.

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Genus Brisaster Gray, 1855

Brisaster moseleyi (A. Agassiz, 1881)

(Fig. 6E)

Examined material: MACN-In 43274,

MACN-In 43275, MACN-In 43278, MACN-

In 43279, MACN-In 43281, MACN-In 43282,

MACN-In 43283, MACN-In 43284, MACN-In

43309 (Table 1).

Distribution: B. moseleyi is recorded on

both side of South America, in the southeastern

Pacific Ocean off Chile from 45° S to 54° S, the

Straits of Magellan, and in the SWAO recorded

at Malvinas Islands (Saucède et al., 2020). We

report the first record of B. moseleyi at both the

northwest slope surrounding the MPA-N/BB,

and the Mar del Plata Canyon (Fig. 1H). In

the Southern Ocean recorded at South Orkney

Islands (Saucède et al., 2020).

Depth: From 400 m (Saucède et al., 2020)

to 2 212 m depth (this study) (Table 1).

Remarks: According to Saucède et al.

(2020) the known geographic and bathymetric

limit for B. moseleyi was the Malvinas (Falk-

land) Islands in the SWAO and 1 400 m depth,

respectively. Here we report the northernmost,

as well as the deepest distribution for B. mose-

leyi so far known. The former is the Mar del

Plata Canyon on the Argentine continental

slope (38°01’23’’ S & 53°51’00’’ W), and

the second 2 212 m depth (MACN-In 43281)

(Table 1). In addition, we report its occur-

rence at the northwest slope of the MPA-N/

BB at 642 m depth (MACN-In 43309) (Fig.

1H). While B. moseleyi is a typical deep-sea

species, it should be mentioned that also was

found in the shallow waters from the Strait of

Magellan by Larraín et al. (1999). Thus, the

records here presented confirm for the first

time the presence of B. moseleyi in deep waters

off Argentina, an extraordinary extension to its

geographic and bathymetric range.

Hood and Mooi (1998) pointed out that

examined specimens labelled as B. moseleyi

from Chile (southeastern Pacific Ocean) were

distinct from other B. moseleyi from the Malvi-

nas Islands and Patagonia (SWAO) and con-

sidered them as two distinct taxa termed “B.

moseleyi (north)” and “B. moseleyi (south)”

respectively. Also, their phylogenetic analysis

based in morphological characters revealed that

B. moseleyi (north) is more closely related to

those species of Brisaster from the west coast

of the Americas, while B. moseleyi (south) is

a sister taxon of B. antarcticus (Döderlein,

1906). Brisaster moseleyi (south) and B. ant-

arcticus differ from B. moseleyi (north) by pos-

sessing narrow petals IV and V, and long and

narrow plastron (Hood & Mooi, 1998), these

features were also present in the specimens

treated in this study (Fig. 6E). Besides, follow-

ing the identification key provided by Saucède

et al. (2020) the specimens collected match

well with their B. moseleyi entity, differing

from B. antarcticus by having the apical system

slightly displaced posteriorly, and the posterior

petals short, slightly more than 1/3 the length

of the anterior paired petals (Fig. 6E). Due to

the uncertainty in taxonomic distinctiveness

and to avoid possible futures nomenclature

troubles, the specimens treated in this study are

provisionally assigned to B. moseleyi. Genetic

studies could help reveal the specific valida-

tion of the north/south groups and possible

synonyms, enriched through the inclusion of

samples from the northernmost population of

B. moseleyi found at the Mar del Plata Canyon

on the Argentine continental slope SWAO,

and to reconstruct phylogenetic relationships

among Brisaster species.

Genus Tripylaster Mortensen, 1907

Tripylaster philippii (Gray, 1851)

(Fig. 6F)

Examined material: MACN-In 43271,

MACN-In 43310, MACN-In 43311, MACN-

In 43312, MACN-In 43313, MACN-In 43315,

MACN-In 43316, MACN-In 43317, MACN-In

43318, MACN-In 43319, MACN-In 43320,

MACN-In 43321, MACN-In 43322, MACN-

In 43324, MACN-In 43325, MACN-In 43326,

MACN-In 43327, MACN-In 43328, MACN-In

43329 (Table 1).

Distribution: T. philippii occurs at the

SWAO from 35° S up to the southeastern

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Pacific Ocean at 41° S, including the Strait of

Magellan, Tierra del Fuego, Isla de los Estados,

and Malvinas Islands (Fig. 1I) (Bernasconi,

1964; Fabri-Ruiz et al., 2017). Also recorded at

the South Georgia Islands, and close to Prince

Edward Island (Saucède et al., 2020).

Depth: From the littoral to 600 m depth

(Saucède et al., 2020).

DISCUSSION

The family Palaeotropidae comprises six

genera including the new genus here described.

Comparing structural features and shape of

the test, development of petals, the shape of

peristome, and aboral tuberculation, Corparva

gen. nov. conform within the Palaetropidae.

Besides, Corparva gen. nov. can be differ-

entiated from the rest Palaeotropidae by its

apical system semi-ethmolytic and its labral

plate reaching to rear part of second adjacent

ambulacral plate. C. lyrida sp. nov. is known

only from abyssal depths at the Mar del Plata

Canyon on the Argentine continental slope, and

it is sympatric with others spatangoids herein

treated. This new genus and species represent

the first report on the family Palaeotropidae

from Argentina.

Many authors have pointed out the high

incidence of benthic marine invertebrates with

non-pelagic development and high rates of

parental care in the SWAO and the Southern

Ocean (Poulin & Féral, 1996, 1998; Pearse,

Mooi, Lockhart & Brandt, 2009), and echi-

noids are not an exception. Although spe-

cies of the genera Brisaster, and Tripylaster

are broadcast spawners with indirect develop-

ment through planktotrophic larvae, members

of the genera Abatus, Tripylus, Parapneustes

and Delopatagus are brooders and present a

lecithotrophic development (Mortensen, 1951;

Pearse & Cameron, 1991; Poulin & Féral,

1996; Gil, Zaixso & Tolosano, 2009). Also, the

distinction between sexes in echinoids is fre-

quently expressed by sexual dimorphism, such

as the form of genital papillae and the size of

genital pores (among others). Mostly in brood-

ing spatangoids, the females present extreme

secondary sexual features associated with this

reproduction strategy, such as the modifica-

tion of the aboral region of the test into mar-

supial brood pouches that give protection for

the development of embryos and juveniles

(David & Mooi, 1990; Gil, Zaixso & Tolosano,

2020). The depressed ambulacra as an aboral

brooding system were widely described for

different spatangoids taxa (Mortensen, 1951;

Philip & Foster, 1971; Schinner & McClintock,

1993). Corparva lyrida sp. nov presents large

gonopores and the paired ambulacra are deeply

depressed forming rounded pouches. A leci-

thotrophic developmental mode for the species

can be suspected, due to large gonopores is

associated with the production of large yolky

eggs (Pearse & Cameron, 1991). The apical

system of C. lyrida sp. nov is sunken with

respect to the extreme of the interambulacral

areas and the ambulacral pouches are slightly

deeper than the apical system as well, form-

ing a wide sunken cruciform area (Fig. 3A).

This area is cover by long primary spines that

emerge leaned over towards the center of the

animal body from the upper external edges of

the ambulacral plates and surrounding interam-

bulacral plates, and by pedicellariae (Fig. 2A),

resulting in a protected chamber. Although no

embryos, nor juveniles were found into the

chamber, the morphological features previously

mentioned suggesting that the specimen could

be a female with marsupial brood chamber

Although is necessary to increase the sam-

pling effort and use a proper experimental

design to conclude on biogeographical issues,

from this study some exploratory trends can be

observed in the distribution of the spatangoids

here studied (Fig. 1). The species composition

in the SWAO has sub-Antarctic and Antarctic

affinities. This could be explained in part by

the presence of water masses formed in these

regions of the world and they are carried to

the SWAO by the MC, which could be acting

as a dispersal vector of propagules and larvae.

Recently studies about biogeographical pat-

terns and benthic eco regionalization based on

echinoids from the Southern Ocean, highlights

the strongly faunal affinities between South

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helpful comments by four anonymous review-

ers. We thank Fabián Tricárico for his assis-

tance with the SEM and to Daniel Lauretta for

facilitating the camera and lens. We acknowl-

edge the Consejo Nacional de Investigaciones

Científicas y Técnicas (CONICET) of Argen-

tina, to which JNF belong as a PhD fellow, and

PEP and MIB as members of the “Carrera del

Investigador Científico y Tecnológico”. This

work is the contribution N° 44 to the Área

Marina Protegida Namuncurá (MPA-N/BB,

Ley 26.875).

RESUMEN

Erizos corazón de las profundidades: Corparva lyrida

gen. et sp. nov. (Palaeotropidae) y nuevos registros

para el Océano Atlántico sudoccidental

Introducción: Los erizos de mar del orden Spatan-

goida son el grupo más diverso de equinoideos recientes.

Objetivo: Describir un nuevo género y una nueva especie

de Spatangoida de profundidades abisales, y reportar

nuevos registros para especies conocidas. Métodos: Los

ejemplares fueron recolectados durante varias expedicio-

nes a diferentes áreas del Océano Atlántico sudoccidental

(OAS), entre las latitudes 37-55° S y abarcando profun-

didades desde 55 a 3 000 metros. Presentamos análisis

morfológicos y de ultraestructura. Resultados: Corparva

lyrida gen. et sp. nov. (Palaeotropidae) fue descripta para

el cañón submarino Mar del Plata en el talud continental de

Argentina (2 950 m de profundidad), el primer registro de

esta familia para Argentina. Corparva gen. nov. difiere en

tener un sistema apical semi-etmolítico y labrum que llega

a la parte posterior de la segunda placa ambulacral adya-

cente. También informamos la distribución más septen-

trional y el registro más profundo para Brisaster moseleyi

(latitud 38° S, 2 212 m de profundidad), la extensión hacia

el norte del rango de distribución de Tripylus excavatus

(latitud 39° S, 74 m de profundidad) y el primer registro

de Abatus philippii y Abatus agassizii en el Banco Burd-

wood/AMP Namuncurá. Conclusiones: El presente trabajo

aporta datos novedosos y actualizados sobre la diversidad

y distribución de erizos de mar espatangoideos del OAS,

incluyendo la descripción de C. lyrida gen. et sp. nov., y

nuevos registros para especies conocidas. Esto muestra

cuánto queda por conocer sobre la diversidad y distribu-

ción de los erizos corazón en el OAS, especialmente de las

profundidades marinas.

Palabras clave: Atelostomata; erizos de mar; mar profun-

do; diversidad; Argentina; AMP-N/BB.

America and sub-Antarctic islands, possibly

due to the connectivity by the flow of the Ant-

arctic Circumpolar Current (Pierrat, Saucède,

Brayard & David, 2013; Fabri-Ruiz, Danis,

Navarro, Koubbi, Laffont & Saucède, 2020).

However, is interesting to highlight that C.

lyrida sp. nov. was found at 2 950 m depth at

the Mar del Plata Canyon on the Argentine con-

tinental slope, and in this region between 2000

to 3000 m there is present the North Atlantic

Deep Water (Voigt et al., 2013), which is origi-

nated at the North Atlantic Ocean, and flush

southward along the continental slope of the

American continent (Piola & Matano, 2001)

The present work brings novel and updated

data about the diversity and distribution of spa-

tangoid sea urchins from the SWAO, including

the description of C. lyrida a new genus and

species from abyssal waters off Argentina, new

records, and occurrence of species previously

reported. This reveals that there is still much

to know about the diversity and distribution of

heart urchins in the SWAO, especially from the

deep-sea. Moreover, the knowledge in these

aspects will contribute to clarify the matted

phylogenetic and evolutionary relations among

the Spatangoida taxa.

Ethical statement: authors declare that

they all agree with this publication and made

significant contributions; that there is no con-

flict of interest of any kind; and that we fol-

lowed all pertinent ethical and legal procedures

and requirements. All financial sources are

fully and clearly stated in the acknowledge-

ments section. A signed document has been

filed in the journal archives.

ACKNOWLEDGMENTS

We are grateful to the different crews of

the R/V Puerto Deseado, and the scientific

staff involved in each cruise. JNF would like to

thank Carlos Conejeros-Vargas for his obser-

vations that enriched an early version of this

work. The final version greatly benefitted from

Revista de Biología Tropical, ISSN electrónico: 2215-2075, Vol. 69(S1): 14-34, March 2021 (Published Mar. 30, 2021)

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