You will be given a definition of a task first, then some input of the task.
In this task, you are given two sentences in the English language (Sentence 1 and Sentence 2). Your task is to identify the connecting word between the two sentences.

Sentence 1:Subsequent descriptions and redescriptions have ensured that the phylogeny of the clade is rather robust at the genus level . Sentence 2:Yet , a comprehensive species - level phylogenetic analysis has proven impossible due to the large amount of species based on scant and fragmentary fossilised material .
Output:
yet