Phylo heterochaetus, Sun & Yu & Li, 2021
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publication ID |
https://dx.doi.org/10.3897/zookeys.1068.71925 |
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persistent identifier |
https://treatment.plazi.org/id/A2E7DB98-6B78-5109-BE12-E30E45C24BEC |
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treatment provided by |
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scientific name |
Phylo heterochaetus |
| status |
sp. nov. |
Phylo heterochaetus sp. nov.
Figures 1 View Figure 1 , 2 View Figure 2 , 3 View Figure 3
Material examined.
Holotype: MBM286984: nYS, Sta. 3875-04, 38°45'N, 123°30'E, 64 m, 16 Dec. 2015. Paratype: MBM286985: nYS, Sta. 16, 39°07'N, 122°54'E, 31 m, 18 Dec. 2016 GoogleMaps . MBM286986: nYS, Sta. C3, 39°00'N, 122°55'E, 45 meters, 18 Dec. 2016 GoogleMaps . Sta. MBM286987: nYS, Sta. A 1, 39°05'N, 122°35'E, 36 m, 18 Dec. 2016 GoogleMaps . MBM023255: nYS, Sta. 2049, 122°45'N, 38°09'E, 51 m, coll. Mu Chen. 11 Jul. 1959 .
Additional material.
MBM023221: nYS, Sta. 2056, 38°30'N, 123°30'E, 63 m, Mu Chen. 15 Apr. 1959 GoogleMaps . MBM009975: nYS, Sta. 2057, 38°00'N, 123°30'E, 70.5 m, coll. Yuheng Cui. 1 Oct. 1958 GoogleMaps . YCTU000004: nYS, Sta. A3, 39°00'N, 122°35'E, 35 m, 18 Dec. 2016 GoogleMaps . YCTU000005: nYS, Sta. 48, 39°16'N, 123°18'E, 37 m, 18 Dec. 2016 GoogleMaps .
Description.
All specimens incomplete, posterior end missing, holotype with 60 chaetigers, 34 mm long and 5 mm wide. Body elongate, about same width throughout; thorax depressed, abdomen cylindrical.
Prostomium short, conical, tapering to rounded tip; eyepots absent, nuchal organs narrow groove at junction with peristomium (Fig. 1 View Figure 1 ). Peristomium a narrow asetigerous segment, distinctly separated from prostomium and chaetiger 1; mouth with anterior oral lip arising from posterior margin of peristomium, posterior oral lip from anterior margin of chaetiger 2. Holotype with proboscis everted, consisting of two large, inflated lobes (Fig. 1 View Figure 1 ).
Holotype with 21 thoracic chaetigers, divided into anterior and posterior sections: anterior thorax with 13 chaetigers (Figs 1 View Figure 1 , 2A View Figure 2 ), posterior thorax with modified spines beginning on chaetiger 14 continuing over 8 chaetigers. Intersegmental annulations first present from chaetiger 1, well developed (Figs 1 View Figure 1 , 2A View Figure 2 ). Thoracic notopodial postchaetal lobe arising from narrow base, broadly triangular, narrowing apically (Fig. 2B View Figure 2 ), becoming long and narrow in abdominal chaetigers (Fig. 2C, D View Figure 2 ). Thoracic neuropodia thick, elongate, fringed, bearing rows of uncini and several capillaries. First chaetiger with 2 rounded postchaetal lobe, increasing to 13-14 on middle thoracic chaetigers (Fig. 2A View Figure 2 ), then decreasing to 6 or 7 on last thoracic chaetigers. Subpodial lobes or stomach papillae from chaetiger 12, numbering 1 at first, then extending to ventral midline on chaetigers 18-25, then abruptly absent (Figs 1 View Figure 1 , 2A View Figure 2 ). Abdominal neuropodia bilobed, with inner lobe blunt, outer lobe cirriform (Fig. 2C, D View Figure 2 ). First abdominal chaetiger with 6 extra lobes or ventral cirri ventral to neuropodium, then reduced to 2 on following 3 chaetigers and 1 or 2 on subsequent chaetigers (Fig. 2C, D View Figure 2 ). Interramal cirrus absent.
Branchiae from chaetiger 5, on anterior chaetigers short, triangular, tapering to narrow papillate rounded apex (Fig. 2B View Figure 2 ), then becoming narrower and longer, leaf-like and ciliated (Fig. 2C, D View Figure 2 ).
Thoracic notopodia with fascicles of crenulated capillaries. Abdominal notopodia with few long, thin capillaries, 2-4 furcate chaetae and 3-5 imbedded aciculae, furcate chaetae with unequal tynes, each tyne with fine needles directed medially, shaft with transverse rows of barbs (Fig. 3E View Figure 3 ).
Anterior thoracic neuropodia with 4 rows and 1 short posterior rows of yellow uncini, and posterior row of crenulate capillaries (Figs 2E View Figure 2 , 3A, B, E, F View Figure 3 ). Anterior 2 rows mixed with 10-12 subuluncini, last row with 7-9 uncini, curved ventrally to anterior rows (Fig. 3A, B View Figure 3 ). Uncini of first 1-4 rows short, with blunt-tipped apex, with 10-18 transverse rows of blunt barbs on convex side, with conspicuous groove apically (Fig. 3B, D View Figure 3 ); uncini of last row longer than anterior ones, only located in ventral side of neuropodium (Fig. 3A View Figure 3 ); subuluncini resemble uncini, but with distally pointed tip, with more than 30 rows of blunt barbs, surrounded by sheath (Fig. 3B View Figure 3 ). Posterior thoracic neuropodia with 4-7 modified spines (Fig. 3C View Figure 3 ), single short row of uncini and 1 or 2 rows crenulate capillaries. Modified spines large, hastate, superior one projecting from neuropodium, with glandular pouch (Fig. 3C View Figure 3 ). Abdominal neurochaetae including 4-6 thin capillaries and single acicula, thin and imbedded.
Anterior thoracic neuropodia with 5 or 6 rows of yellow uncini and posterior row of crenulate capillaries (Figs 2E View Figure 2 , 3A, B View Figure 3 ). Anterior 2 rows mixed with 10-12 subuluncini, last row with 7-9 uncini, curved ventrally to anterior rows (Fig. 3A, B View Figure 3 ). Uncini of anterior 4 or 5 rows short, with blunt-tipped apex, with 10-18 transverse rows of blunt barbs on convex side, with conspicuous groove apically (Fig. 3B, D View Figure 3 ); uncini of last row longer than anterior ones, only located in ventral side of neuropodium (Fig. 3A View Figure 3 ). Subuluncini resemble uncini but with distally pointed tip, with more than 30 rows of blunt barbs, surrounded by sheath (Fig. 3B View Figure 3 ). Posterior thoracic neuropodia with 4-7 modified spines (Fig. 3C View Figure 3 ), single short row of uncini and 1 or 2 rows crenulate capillaries. Modified spines large, hastate, superior one projecting from neuropodium (Fig. 3C View Figure 3 ). Abdominal neurochaetae including 4-6 thin capillaries and single acicula, thin and imbedded.
Pygidium not observed.
Variation.
One paratype (MBM286986) with 13 and 14 anterior thoracic chaetigers on left and right side respectively, posterior thorax with 9 and 8 chaetigers, respectively. Holotype and other specimens with 13 anterior thoracic chaetigers, posterior thorax with 4-8.
Etymology.
The species is named for the thoracic neuropodia with two kinds of uncini.
Type locality.
Northern Yellow Sea, China.
Remarks.
This species is unusual in the genus in having anterior thoracic neuropodia with 5 or 6 rows of uncini intermixed with a few subuluncini in the first 1 or 2 rows. Phylo heterochaetus sp. nov. is similar with P. ornatus (Verrill, 1873) for: 1) anterior thoracic neuropodia with rows of uncini, 2) lacking interramal cirri, 3) anterior thorax with 13 or 14 chaetigers. They can be easily distinguished by 1) species of P. heterochaetus sp. nov. with 4-8 posterior thoracic chaetigers, while the latter species with 13 or more chaetigers; 2) species of P. heterochaetus sp. nov. with 10 or 11 subuluncini intermixed with first 2 rows uncini, while the latter species lacks subuluncini; 3) modified spines hastate in P. heterochaetus sp. nov. and acicular in P. ornatus .
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