Mixtodiaixis Markhaseva & Renz, 2025

Genus Mixtodiaixis Markhaseva & Renz gen. nov.

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Diagnosis (females and males). The combination of 4 setae with 5 teeth at the mandible gnathobase cutting edge is an apomorphie for the genus. The following combination of characters define Mixtodiaixis gen. nov. among “Bradfordians”: 1) rostrum as a bilobed plate; 2) oral parts nearly identical in females and males; 3) antenna exopod setal formula 0,0-0-0,1,1,1,1,1,3; 4) mandible, basis with 3 setae; exopod 5-segmented with 1, 1, 1, 1, and 2 setae; endopod segment 2 with 9 setae; 5) maxillule praecoxal arthrite with 7 terminal spines, anterior and posterior setae absent, coxal endite with 2 setae; coxal epipodite with 9 setae; proximal basal endite with 4 setae, distal basal endite with 4 setae; endopod with 8 setae; exopod with 7–8 setae; 6) maxilla endites setal formula 4, 3, 3, 3 and 4 setae, proximal basal endite with 2sc+1w setae and distal basal endite with 2sc+1w setae, endopod with 3 worm-like and 6 brush-like setae, and 7) maxilliped syncoxa with praecoxal setal formula: 1w, 2 (1sc+1w), and 3 (2sc+1br) setae and 2 setae on coxal endite, endopod segment 1 with 3 setae. P1–P4 of typical clausocalanoidean setation and segmentation. P 5 in females uniramous, symmetrical, 3-segmented, lacking terminal and lateral spines. P 5 in males nearly reaching urosome somite 3, of simple structure, uniramous, 5-segmented.

Etymology. The generic name is combined from the Latin “mixto”, meaning mixture, that indicates that the described genus possesses characters typical for Diaixidae and selected features of other “Bradfordians”.

Type species Mixtodiaixis kurambiohadalis sp. nov., by monotypy.

Remarks. The new genus Mixtodiaixis gen. nov. fits the diagnosis of Diaixidae ( Markhaseva et al., 2014) , however, shares some characters with other Bradfordian genera, e.g., 1) maxillule praecoxal arthrite with 7 terminal spines a new genus shares with Diaiscolecithrix Markhaseva, Schulz & Renz, 2010 ( Scolecitrichidae ) and unresolved genus Heteromalla Sars, 1907 vs 9 terminal spines present in nearly all other “Bradfordians”; 2) maxilla basal endites with 2sc+1w setae Mixtodiaixis gen. nov. shares with some species of Xanthocalanus Giesbrecht, 1892 and Brachycalanus Farran, 1905 ( Phaennidae ), unresolved genus Puchinia Vyshkvartzeva, 1989 , and Ranthaxus Markhaseva & Schulz, 2010 ( Diaixidae ) vs other “Bradfordians” lacking worm-like sensory setae at both endites; 3) maxilliped coxal endite with 2 setae a new genus shares with Rostrocalanus Markhaseva, Schulz & Martinez Arbizu, 2008 ( Rostrocalanidae ) vs 3 setae typical of nearly all “Bradfordians”, and 4) maxilliped endopod segment 1 with 3 setae a new genus shares with Rostrocalanus and unresolved genus Bradfordiella Andronov, 2007 vs 4 setae typical of nearly all “Bradfordians”.