def allosaurus_to_list(filename):
    output = []
    with open(filename) as f:
        for l in f.readlines():
            line = l.strip().split(" ")
            output.append([line[0], line[2]])
    return output

%%writefile test.txt
0.510 0.045 n
0.600 0.045 i
0.900 0.045 a
0.990 0.045 l
1.050 0.045 d
1.110 0.045 pʲ
1.170 0.045 a
1.290 0.045 j
1.410 0.045 d

Writing test.txt

l = allosaurus_to_list("test.txt")

starts = ['0.00'] + [f[0] for f in l[0:-1]]

massaged = 

['0.00',
 '0.510',
 '0.600',
 '0.900',
 '0.990',
 '1.050',
 '1.110',
 '1.170',
 '1.290']