Diagnosis. Asterocheridae. Body dorsoventrally flattened. Prosome ovoid or discoid, urosome cylindrical and 4- segmented in female. Antennule of female basically 19-segmented with large aesthetasc on 17th segment; ancestral segments IX –XIII fused; distal 3 segments frequently fused to become 1 or 2 segments. Antenna with 1-segmented exopod and 3-segmented endopod bearing distal claw. Oral cone short or elongated, siphon-like. Mandible consisting of stylet and 1- or 2-segmented palp bearing two distal setae. Maxillule bilobed. Maxilla 2-segmented; distal segment forming curved claw. Maxilliped with 6-segmented. Legs 1–4 with 3-segmented exopod and endopod. Free segment of leg 5 with 2 or 3 setae.
Remarks. Kim (2010) proposed a new definition for Asterocheres, with the main diagnostics characters related to leg setation and number of antennule segments posteriorly to aesthetasc. Thus, the author restricted the number of valid species in Asterocheres and many species were considered as species inquirendae. Since then, new species of Asterocheres were described ( Crescenti et al. 2010; Varela 2010, 2012; Kim & Min 2013) and redescriptions were published ( Conradi & Bandera 2011; Bandera & Conradi 2013; Bandera & Conradi 2014). Although the new species being described shows the leg setation established by Kim for Asterocheres, the antennule segmentation highlights a relevant difference in the fusion pattern. Neoasterocheres gen. nov. can be distinguished from Asterocheres by having the fusion of antennule ancestral segments IX –XIII resulting in the aesthetasc located on the 17th segment, with 3 distal segments frequently fused to become 1 or 2. Kim (2010) stated that the female antennule is basically 21-segmented because depending on the existence of distal fusions the amount of segments can be reduced to 19, however these fusions occurs between the last 3 segments, which are posterior to ancestral segment XXI. When Kim (2010) established that the aesthetasc is located on segment 18 in Asterocheres, the author excluded the possibility of occurrence of other additional fusions previous to the 18th segment, and disregarded the existence of species presenting fusions of additional ancestral segments.
According to Huys & Boxshall (1991) on the ancestral pattern of a siphonostome antennule, segment XXI is characterized by the presence of an aesthetasc additional to the maximum armature of two setae found in an unfused segment. Therefore, the authors highlighted the presence of a group of setae on ancestral segment IX, thus indicating a fusion involving at least segments IX –XII. This is expressed in a maximum of 8 setae present on the segment and the existence of eight free single segments between this compound segment (IX –XII) and the one bearing the aesthetasc (XXI). The presence of less than eight free segments between these two landmarks indicates the occurrence of further fusions in the section. Besides that, a spine is commonly present on ancestral segment XIV, and may constitute another relevant landmark. In Asterocheres we found a segment between the compound segment (IX –XII) and the segment bearing a spine (XIV), thus indicating that ancestral XIII segment is free. In the new genus the segment with a spine (XIV) is close to the compound segment (IX –XII). The ancestral segment XIII is not free, it is fused with the previous segment (IX –XII). This pattern can be confirmed by the existence of only seven free segments between the original IX –XII and the XXI, and by the absence of any double segment between these two landmarks, which would be indicated by the presence of four setae and a segment with a length twice its regular size.