SDSM 64281, also known as „Ornithurine C“ is mentioned in a study from 2011 that deals with the extinction of several bird clades at the end of the Cretaceous. 
This form is apparently known from at least one fragmented coracoid and comes from a bird that in life must have had a weight of about 3 kg. Unfortunatley the study fails to inform if this form is known from only the aforementioned single coracoid, and if not, if its remains were recovered only from the earliest Paleocene layers or if they were also recovered from the lates Cretaceous layers as it is the case with all other bird remains in the study.:
„One of these species, Ornithurine C, is [also or only?] known from the Paleocene and therefore represents the only Maastrichtian bird known to cross the K–Pg boundary.“
Apparently, this species is known from at least four coracoids or remains of such, and they are named as „SDSM 64281A“, „SDSM 64281B“, „UCMP 175251“, and „MOR 2918“ and most are indeed of Late Cretaceous age, but just not all of them.
According to the authors this species might be identical with a species that was named as Graculavus augustus Hope, a bird that apparently belongs to the Charadriiformes but was very much unlike any of the charadriiform birds living today, in life it may have appeared like some kind of giant stone-curlew aka. thick-knee. 
 Nicholas R. Longrich; Tim Tokaryk; Daniel J. Field: Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary. PNAS 108 (37) 15253-15257. 2011
 Nicholas R. Longrich; Tim Tokaryk; Daniel J. Field: Mass extinction of birds at the Cretaceous-Paleogene (K-Pg) boundary. PNAS 108 (37) 15253-15257. 2011. Supplementary Information