大洋龙亚科（Halisaurinae）属于沧龙科，由Bardet等人于2005年所创立，是群多样化的海生有鳞目动物，生存于晚白垩纪。大洋龙亚科的词源来自于大洋龙（Halisaurus），在希腊文中意为「海蜥蜴」。

Bardet等人将大洋龙亚科鉴定为：沧龙类之中，亲缘关系接近于大洋龙，而离莫那龙较远的所有物种。大洋龙亚科的明确特征为：前上颌骨与上颌骨之间的缝合处前部垂直，中间倾斜，后部水平、颅顶骨与鳞状骨之间的接触面倾斜、桡骨的轴前隆起占了长度的2/3、胫骨与腓骨长而修长，末端稍微扩张。大洋龙亚科的不明确特征则包含：额骨前2/3部分有背侧中央隆起、额骨腹侧有突起物、顶孔（Parietal foramen）由腹侧突起物包围、方骨有大型蹬下突、方骨的蹬下突与蹬上突合并、没有椎弓突（Zygosphene）-椎弓凹（Zygantrum）复合体、以及愈合的脉棘。

Halisaurinae is a subfamily of mosasaurs, a diverse group of Late Cretaceous marine squamates.

Bardet et al. (2005, p. 464) diagnosed the Halsaurinae as all mosasaurs more closely related to Halisaurus than Moanasaurus. Unambiguous character states were listed as follows: "premaxilla-maxilla sutural contact vertical anteriorly, oblique at midpoint and horizontal posteriorly; contact plane between the parietal and the supratemporal oblique; preaxial ridge extending on two-thirds of the length of the radius; tibia and fibula long and slender with slightly expanded extremities. Ambiguous characters include "dorsal median ridge borne on the anterior two-thirds of the frontal; frontal with ventral boss; parietal foramen surrounded by a ventral boss; quadrate with large infrastapedial process; coalescent infra- and suprastapedial processes of quadrate; zygosphene-zygantrum complex absent; synapophyses of the cervical vertebrae extending ventrally to the ventral surface of the centrum; fused haemal spines."