I have made this poncho once before, it's a good design as it stay's on and in place unlike the regular poncho. It's perfect for the toddler/child for this reason.
For the top photo I used 110 gm's of yarn and a size 4.00 mm hook (US G/6)
The center length measure's approx 13 inches (with out the tassels).
You can find the free pattern here, but I did have some difficulty in understanding row's 4 and 14 for the size 12/15 months, I will include my revised steps below in red.
half shell: 2dc ch 1
Shell: 2 dc, ch1, 2 dc
Rnd4: Ch 3, dc, ch 1, 2 dc in same stitch, ch 1,** skip 2 stitches, 2 dc, ch 1 in next stitch. skip 1 stitch, 2 dc, ch 1 in next stitch ** repeat from ** to** for a total of 14 half shells.skip 2 st’s, Shell in next stitch, skip 2 st’s, than repeat with half shells alternating with skipping 2 stitches and 1 stitch in between each around(14half shells) Join: total of 28 half shells and 2 shells
Rnd 14: slip stitch to center of shell, Ch 2, dc, ch 1, 2dc in ch 1 sp.** ch 1, 2dc in next ch 1 sp ** repeat till after you have done 6- 1/2 shells Now
skip 12 shell spaces,(armhole) 2dc,ch 1 in next ch 1 sp, repeat 5 more times (6-1/2 shells) do a full shell, ** Repeat from** to last shell, join..